RECONFIGURABLE MODULAR FURNITURE SYSTEM The invention relates to a reconfigurable modular furniture system, preferably for babies, toddlers and young children. It is known to use modular furniture. According to a first aspect of the invention, there is provided a reconfigurable modular furniture system comprising first and second furniture components, each of the first and second furniture components including a base portion and a sidewall portion, the sidewall portion arranged on or around the base portion, wherein the first and second furniture components are configured to be releasably stackable on top of each other to form a seat unit or shelf unit, wherein the first and second furniture components are configured to be releasably coupleable to each other to form a bed unit. The features of the reconfigurable modular furniture system according to the invention enables the formation of a variety of furniture units. In particular, the ability to form a seat unit or shelf unit and the bed unit allows the reconfigurable modular furniture system to be used for a growing child, preferably from baby to toddler to young child. This not only provides continuity for the child in terms of familiarity with the furniture and the system’s overall decorative aesthetic but also provides cost and space savings in comparison to regularly buying new furniture that will be quickly outgrown by the child as they age. Furthermore, the reconfigurable modular furniture system can be re-used for a new-born child in the same way as for the previous child. It will be appreciated that the first and second furniture components may be configured to be releasably stackable on top of each other to form the seat unit in one stacking configuration and form the shelf unit in another stacking configuration. For the purposes of the specification, the term “couple” is intended to encompass direct physical connection or indirect physical connection via one or more intermediate parts, the term “releasably” is intended to mean that the described parts can be separated after being brought, coupled or connected together, the term “seat unit” is an item of furniture designed for sitting (e.g. a chair), the term “shelf unit” is an item of furniture for storage or display of objects, and the term “bed unit” is an item of furniture that is designed for lying or sleeping. The sidewall portion may be configured in a variety of ways, e.g. for functional or aesthetic purposes, so long as it is arranged on or around the base portion. The sidewall portion may be attached to the base portion or may be integral with the base portion. The sidewall portion may include a plurality of slats or bars that are spaced apart from each other. The slats or bars are for providing visibility of the child through the sidewall portion and for weight reduction. The sidewall portion may be arranged along part of a perimeter of the base portion. The sidewall portion may be a curved sidewall portion and/or a three-sided sidewall portion. The base portion may be detachable from the sidewall portion. When forming one or more furniture units (e.g. a table unit, a chair unit, a transport vehicle unit) of the reconfigurable modular furniture system, the base portion may be detached from the sidewall portion, turned over and then reattached to the sidewall portion. This may be carried out to hide features (such as fastener holes) present on one side or surface of the base portion. In embodiments of the invention, the first and second furniture components may be configured to be releasably stackable on top of each other to form the seat unit in which the base portions of the first and second furniture components are stacked on top of each other to form a sitting surface of the seat unit. In such an embodiment, the sidewall portion of one of the first and second furniture components may form a seat back, and optionally seat armrests, of the seat unit while the sidewall portion of the other of the first and second furniture components may form a base underneath the sitting surface. In further embodiments of the invention, the first and second furniture components may be configured to be releasably stackable on top of each other to form the shelf unit in which the base portion of each of the first and second furniture components forms a respective shelf surface of the shelf unit. In such an embodiment, the sidewall portion of each of the first and second furniture components may form a respective shelf wall of the shelf unit. In still further embodiments of the invention, the first and second furniture components may be configured to be releasably stackable on top of each other to form the seat unit in a first stacking configuration in which the base portions of the first and second furniture components are stacked on top of each other to form a sitting surface of the seat unit, and wherein the first and second furniture components may be configured to be releasably stackable on top of each other in to form the shelf unit in a second stacking configuration in which the base portion of each of the first and second furniture components forms a respective shelf surface of the shelf unit. Different bed units may be formed by the first and second furniture components. For example, the bed unit may be a cot or crib. To enable a variety of sizes and appearances of the bed unit, there are different ways of coupling the first and second furniture components to form the bed unit, non-limiting examples of which are described as follows. The first and second furniture components may be configured to be releasably and directly connectable to each other to form the bed unit. This may be achieved by configuring the sidewall portions of the first and second furniture components to be releasably and directly connectable to each other to form the bed unit and/or by configuring the base portions of the first and second furniture components to be releasably and directly connectable to each other to form the bed unit. The reconfigurable modular furniture system may include a floor portion, which is releasably placeable on the base portions of the first and second furniture components when the bed unit is formed. The floor portion may be configured to be releasably fastenable (e.g. screwed) to the base portions or may be placeable on the base portions without fastening. In this way the floor portion forms a support surface for a child in the bed unit. The floor portion may be made of a hard material or a soft material. The reconfigurable modular furniture system may include a plurality of floor portions of different sizes, each of which is used in different bed units formed by the first and second furniture components. The reconfigurable modular furniture system may include at least one attachment member. The first and second furniture components may be configured to be releasably coupleable to each other via the or each attachment member to form the bed unit. Preferably the sidewall portions of the first and second furniture components are configured to be releasably coupleable to each other via the or each attachment member to form the bed unit. The or each attachment member may be an additional sidewall portion. The or each additional sidewall portion may have the same height as the sidewall portions of the first and second furniture components. The or each attachment member is preferably an elongate attachment member, e.g. a strap, bar or rod, but may take other forms in other embodiments. In embodiments of the invention, the reconfigurable modular furniture system may include a floor component that is configured to be releasably placeable between the first and second furniture components to form a floor of the bed unit. The floor component may be configured to be releasably placeable on the aforementioned floor portion between the first and second furniture components to form the floor of the bed unit. The floor component may be a rigid floor component, e.g. a wooden floor component. Alternatively the floor component may be a mat. Preferably the mat is configured to be releasably placeable between the first and second furniture components to combine with the sidewall portions to form a wall of the bed unit. The mat on its own may be used as an activity mat for the child. In further embodiments of the invention, the reconfigurable modular furniture system may include at least one support leg that is configured to be releasably coupleable to at least one of the first and second furniture components. The reconfigurable modular furniture system may include at least one support leg that is adjustable to change its height (e.g. a telescopic support leg or a multi-part leg). The reconfigurable modular furniture system may include a plurality of support legs. Each of the plurality of support legs may be configured to be releasably coupleable to a respective corner of the bed unit formed by the first and second furniture components. The reconfigurable modular furniture system may include a plurality of support legs of different lengths, which may be used for placing the bed unit on uneven surfaces or adjusting the height of the bed unit to accommodate different user heights, preferences and/or needs (such as ease of putting a child into the bed unit and removing the child from the bed unit). In still further embodiments of the invention, the reconfigurable modular furniture system may include at least one wheel (such as a caster wheel or swivel wheel) that is configured to be releasably coupleable to at least one of the first and second furniture components. Preferably the reconfigurable modular furniture system includes a plurality of wheels. This provides the formed furniture unit with limited or full mobility depending on the number of wheels and the configuration of the or each wheel. The or each wheel may be configured to be releasably coupleable to the base portion of at least one of the first and second furniture components. The or each wheel may be configured to be releasably coupleable to a base of the or the respective support leg. In this way, the or each wheel supports the or the respective support leg. The first and second furniture components may be configured to be releasably coupleable to each other to form a transport vehicle unit, such as a cart or trolley. When the reconfigurable modular furniture system includes a plurality of wheels, each wheel may be configured to be releasably coupleable to a respective corner of the transport vehicle unit formed by the first and second furniture components. In embodiments of the invention, the reconfigurable modular furniture system may include at least one base portion support structure. The or each base portion support structure may be configured to be releasably stackable below either or both of the base portions of the first and second furniture components. This enable the elevation of either or both of the first and second furniture components to adjust their height above ground, which in turn provides additional variety in the type of furniture unit that can be formed by the reconfigurable modular furniture system. Furthermore, the reconfigurable modular furniture system may include a plurality of base portion support structures, wherein the base portion support structures may be configured to be releasably stackable on top of each other. In further embodiments of the invention, the reconfigurable modular furniture system may include at least one sidewall portion extender. The or each sidewall portion extender may be configured to be releasably stackable on or below either or both of the sidewall portions of the first and second furniture components. This enables an increase in height or depth of either or both of the sidewall portions of the first and second furniture components, which in turn provides additional variety in the type of furniture unit that can be formed by the reconfigurable modular furniture system. The or each sidewall portion extender can be freely installed in or omitted from the furniture units formed by the reconfigurable modular furniture system, thus providing greater variety in the designs of the furniture units. Also, the same sidewall portion extender can be used across different furniture units, which adds to the modularity of the reconfigurable modular furniture system. Furthermore, the reconfigurable modular furniture system may include a plurality of sidewall portion extenders, wherein the sidewall portion extenders may be configured to be releasably stackable on top of each other. In still further embodiments of the invention, the first and second furniture components may be configured to be releasably coupleable to each other to form a table and seat unit in which the base portion of one of the first and second furniture components forms a table top of the table and seat unit and in which the base portion of the other of the first and second furniture components forms a sitting surface of the table and seat unit. In such embodiments, one or more base portion support structures and/or one or more sidewall portion extenders may be used to adjust the height of either or both of the table and seat of the table and seat unit. The first and second furniture components may be configured to be releasably stackable on top of each other to form the seat unit in a first configuration in which the base portions of the first and second furniture components are stacked on top of each other to form a sitting surface of the seat unit, and wherein the first and second furniture components may be configured to be releasably coupleable to each other to form a table and seat unit in a third stacking configuration in which the base portion of one of the first and second furniture components forms a table top of the table and seat unit and in which the base portion of the other of the first and second furniture components forms a sitting surface of the table and seat unit. The first and second furniture components may be configured to be releasably stackable on top of each other in to form the shelf unit in a second stacking configuration in which the base portion of each of the first and second furniture components forms a respective shelf surface of the shelf unit, and wherein the first and second furniture components may be configured to be releasably coupleable to each other to form a table and seat unit in a third stacking configuration in which the base portion of one of the first and second furniture components forms a table top of the table and seat unit and in which the base portion of the other of the first and second furniture components forms a sitting surface of the table and seat unit. The first and second furniture components may be configured to be releasably stackable on top of each other to form the seat unit in a first stacking configuration in which the base portions of the first and second furniture components are stacked on top of each other to form a sitting surface of the seat unit, wherein the first and second furniture components may be configured to be releasably stackable on top of each other in to form the shelf unit in a second stacking configuration in which the base portion of each of the first and second furniture components forms a respective shelf surface of the shelf unit, and wherein the first and second furniture components may be configured to be releasably coupleable to each other to form a table and seat unit in a third stacking configuration in which the base portion of one of the first and second furniture components forms a table top of the table and seat unit and in which the base portion of the other of the first and second furniture components forms a sitting surface of the table and seat unit. The coupling or connection of different parts of the reconfigurable modular furniture system may be carried out by, e.g., fasteners and/or interference-fit connectors (also known as push-fit, press-fit or friction-fit connectors) and/or clearance-fit connectors and/or transition-fit connectors. Non-limiting examples of fasteners include dowel fasteners, screw fasteners, latch fasteners and nut and bolt fasteners. In particular, cam dowel fasteners (also known as minifix furniture fittings) and cam locks may be used in combination. It will be appreciated that the use of the terms “first” and “second”, and the like, in this patent specification (e.g. the first, second and third stacking configurations) is merely intended to help distinguish between similar features, and is not intended to indicate the relative importance of one feature over another feature, unless otherwise specified. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, and the claims and/or the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and all features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner. Preferred embodiments of the invention will now be described, by way of non-limiting examples, with reference to the accompanying drawings in which: Figure 1 shows a reconfigurable modular furniture system according to a first embodiment of the invention; Figures 2 and 3 show a baby crib of the reconfigurable modular furniture system of Figure 1; Figure 4 shows an activity mat of the reconfigurable modular furniture system of Figure 1; Figures 5 and 6 show a cot of the reconfigurable modular furniture system of Figure 1; Figure 7 shows a play cart of the reconfigurable modular furniture system of Figure 1; Figure 8 shows a shelf unit of the reconfigurable modular furniture system of Figure 1; Figures 9 and 10 show a table and seat unit of the reconfigurable modular furniture system of Figure 1; Figure 11 shows a seat unit of the reconfigurable modular furniture system of Figure 1; Figure 12 shows a reconfigurable modular furniture system according to a second embodiment of the invention; Figure 13 shows a reconfigurable modular furniture system according to a third embodiment of the invention; and Figures 14 to 17 show a reconfigurable modular furniture system according to a fourth embodiment of the invention. The figures are not necessarily to scale, and certain features and certain views of the figures may be shown exaggerated in scale or in schematic form in the interests of clarity and conciseness. The reconfigurable modular furniture system is exemplarily described with reference to its use with a growing child but it will be appreciated that the reconfigurable modular furniture system is not limited to use by young children. A reconfigurable modular furniture system according to a first embodiment of the invention is shown in Figure 1. The reconfigurable modular furniture system can be transformed into a variety of furniture units. The transformation may be carried out by adding, removing, replacing and/or rearranging different parts of the reconfigurable modular furniture system. Figures 1a, 2 and 3 show a baby crib 20 which is used by a new-born baby for resting or sleeping. The baby crib 20 includes first and second furniture components 22,24, each of which has a base portion 26 and a sidewall portion 28. The sidewall portion 28 includes a plurality of slats that are spaced apart from each other. In each furniture component 22,24, the sidewall portion 28 is arranged on the base portion 26 to extend along part of the perimeter of the base portion 26 so that it forms an open curved sidewall portion 28. Each end of the sidewall portion 28 includes outer and inner end- faces 30,32, where the inner end-face 32 is recessed away from the outer end-face 30. Holes 34 for receiving threaded cam dowels are formed in the inner end-faces 32. The baby crib 20 includes two sidewall portion extenders 36,38 that are releasably connected to the top surfaces of the sidewall portions 28, so that each sidewall portion extender 36,38 is stacked on a respective one of the sidewall portions 28. The connection is achieved using cam dowel fasteners inserted in holes 34 in the sidewall portion extenders 36,38 and the sidewall portions 28 and securing them using cam locks. The sidewall portion extenders 36,38 are shaped as open curved sidewall portion extenders so that they are similar in shape to the sidewall portions 28. Holes 34 for receiving threaded cam dowels are formed in end-faces 40 at the ends of the sidewall portion extenders 36,38. The sidewall portion extenders 36,38 are removable from the sidewall portions 28. The purpose of the sidewall portion extenders 36,38 is to cover any fastener holes on the sidewall portions 28 for aesthetic and safety reasons. To connect the first and second furniture components 22,24 to each other, the end- faces 30,32 of the first and second furniture components 22,24 are positioned opposite each other before combining the base portions 26 to form a floor of the baby crib 20 and combining the sidewall portions 28 to form a wall of the baby crib 20 so that the base portions 26 and the sidewall portions 28 together form a walled enclosure with an open top. Opposite end-faces 40 of the sidewall portion extenders 36,38 are connected to each other by aligning holes 34 in the opposite end-faces 40 and by inserting cam dowel fasteners in the holes 34 and securing them using cam locks to join the opposite end-faces 40. Opposite inner end-faces 32 of the sidewall portions are connected to each other by locating intermediate wall boards 42 between the inner end-faces 32, by aligning holes 34 in the inner end-faces 32 with holes 34 in the intermediate wall boards 42 and by inserting cam dowel fasteners in the holes 34 and securing them using cam locks to join the inner end-faces 32 to the intermediate wall boards 42. Additionally or alternatively, to connect the first and second furniture components 22,24 to each other, the base portions 26 may be connected to each other by similarly using holes 34, cam dowel fasteners and cam locks. The baby crib 20 includes a crib floor portion 44a that is placed on and releasably fastened to the base portions 26 of the first and second furniture components 22,24. The interconnection of the base portions 28 by the crib floor portion 44a provides the baby crib 20 with additional structural integrity. The baby crib 20 includes four support legs 46,48, each of which is connected to the sidewall portions 28 at a respective corner of the baby crib 20 by using screw fasteners to join the support legs 46,48 to the sidewall portions 28 at the corners of the baby crib 20. The baby crib 20 includes two caster wheels 50 (also known as swivel wheels), each of which is rotatably coupled to a base of a respective support leg 48 of one of the furniture components. The lengths of the support legs 46,48 are such that the baby crib 20 is supported by the support legs 46,48 at an elevated height above ground. In particular, the lengths of the support legs 48 coupled to the caster wheels 50 are shorter than the lengths of the other support legs 46 to account for the heights of the caster wheels 50, so that the support legs 46,48 are balanced to keep the floor of the baby crib 20 at a horizontal level relative to ground. It is envisaged that, in other embodiments of the invention, other types of wheels may be used. It is also envisaged that, in other embodiments of the invention, the caster wheels 50 may be omitted and the support legs 46,48 may have the same length. Figures 1b and 4 show an activity mat 52 on which the child can rest, sleep or play. The activity mat 52 includes a mat body 54 and a pair of flaps 56. The mat body 54 is shaped as a rectangle with semi-circles at its opposite ends (which is known as a stadium or obround shape). The flaps 56 have a rectangular shape and are connected to the sides of the mat body 54. The mat body 54 and flaps 56 can be laid flat on a floor. Figures 1c, 5 and 6 show a cot 58 which is used by a toddler for resting or sleeping. Since the toddler is taller and more mobile than a new-born baby, the baby crib 20 is transformed into the bigger cot 58. Initially the first and second furniture components 22,24 are separated from each other by unfastening and removing the cam dowel fasteners. The first and second furniture components 22,24 are then spaced apart from each other by a gap. The cot 58 includes a cot floor portion 44b which is longer than the crib floor portion 44a of the baby crib 20. The cot floor portion 44b extends across the gap so that it is placed on and releasably fastened to the base portions 26 of the first and second furniture components 22,24. The interconnection of the base portions 28 by the cot floor portion 44b provides the cot 58 with additional structural integrity. The mat body 54 of the activity mat 52 is placed on the floor portion between the first and second furniture components 22,24, so that the mat body 54 forms a floor of the cot 58. In particular, the ends of the mat body 54 overlay the base portions 26 of the first and second furniture components 22,24, while a central section of the mat body 54 extends across the gap between the base portions 26 of the first and second furniture components 22,24. The flaps 56 combine with the sidewall portions 28 to form a wall of the cot 58. In particular, the flaps 56 are vertically positioned so that the sides of the flaps 56 locate against the inner end-faces 32 and that a central section of each flap 56 extends across the gap between the sidewall portions 28 of the first and second furniture components 22,24. Attachment members in the form of straps 60 are used to couple the sidewall portions 28 to each other. In particular, ends of the straps 60 are secured (e.g. using hook- and-loop fasteners) to slots 62 at the ends of the sidewall portions 28 so that the straps 60 extend along the sides of the cot 58 and across the gap between the first and second furniture components 22,24. A central section of each strap 60 is preferably attached to the flaps 56 of the activity mat 52. When the activity mat is laid on the floor for playing, the ends of the straps 60 may be connected and the straps 60 may be kept underneath the activity mat 52. In other embodiments, the straps 60 may be separate from the activity mat 52. Optional additional open curved sidewall portion extenders 64 are stacked on top of the sidewall portions 28 to increase the height of the wall of the cot. The number of sidewall portion extenders 64 may vary depending on the desired height of the wall of the cot 58. Instead of directly connecting the open curved sidewall portion extenders 36,38,64 to each other, the open curved sidewall portion extenders 36,38,64 are instead coupled to each other via intermediate planar sidewall portion extenders 66 by similarly using holes 34, cam dowel fasteners and cam locks. Figures 1d and 7 show a play cart 68 which is a pull cart in the embodiment shown but may be configured as a push cart in other embodiments. As the toddler becomes more mobile, the cot 58 can be transformed into the play cart 68 that can be used by the child for playing. It will be understood that the crib 20 can be transformed into the play cart 68 without requiring an intermediate transformation into the cot 58. The play cart 68 is similar in structure to the baby crib 20, except that the play cart 68 omits the support legs 46,48 and that the play cart 68 includes four caster wheels 50, each of which is connected to the base portions 26 at a respective corner of the play cart 68. In this way the play cart 68 can move around on the caster wheels 50. The use of the intermediate wall boards 42 is optional for the play cart 68. An optional pulling rope 70 is attached to the sidewall portion 28 of one of the furniture components 22,24. The pulling rope 70 includes a handle for use by the child, or by another person if the child is inside the play cart 68. Either or both of the base portions 26 may be detached from the sidewall portions 28, turned over and then reattached to the sidewall portions 28 when forming the play cart 68. This is to hide fastener features (e.g. fastener holes) on one side of the base portions 26 that were used for fastening the crib floor portion 44a or the cot floor portion 44b. Figures 1e and 8 show a shelf unit 72 which is used by the child to store their belongings. To form the shelf unit 72, the first and second furniture components 22,24 are stacked on top of each other. Both furniture components 22,24 are turned upside-down so that their base portions 26 define respective top surfaces of the furniture components 22,24. The lower furniture component 22 is supported on the ground by an optional sidewall portion extender 36. The sidewall portion extender 36 is removable from the sidewall portion 28 of the lower furniture component 22. The sidewall portion 28 of the higher furniture component 24 is releasably connected to the base portion 26 of the lower furniture component 22. Another optional sidewall portion extender 38 is releasably connected to the top of the base portion 26 of the higher furniture component 24. The sidewall portion extender 38 is removable from the sidewall portion 28 of the higher furniture component 24, acts to cover any fastener holes on the sidewall portion 28 for aesthetic and safety reasons, and prevents items from falling off the back and sides of the top surface of the higher shelf component 24. The connections may be achieved using cam dowel fasteners inserted in holes 34 in the connected parts and securing them using cam locks. In this way the first and second furniture components 22,24 form the shelf unit 72 in which the base portion of each of the first and second furniture components forms a respective shelf surface of the shelf unit. When forming the shelf unit 72, either or both of the base portions 26 may require detachment from the sidewall portions 28, turning over and reattachment to the sidewall portions 28 in order to hide fastener features (e.g. fastener holes) on one side of the base portions 26. Figures 1f, 9 and 10 show a table and seat unit 74 that includes a table unit 76 and a seat unit 78. One of the furniture components 22 is turned upside-down to form the table unit 76 so that its base portion 26 defines a table top. The other furniture component 24 is arranged to form the seat unit 78 so that its base portion 26 defines a sitting surface of the seat unit 78 and that its sidewall portion 28 defines a seat back and seat armrests of the seat unit 78. Optional sidewall portion extenders 36,38 may be releasably connected to the table top of the table unit 76 and to the sidewall portion 28 of the seat unit 78. The sidewall portion extenders 36,38 are removable from the sidewall portions 28 and act to cover any fastener holes on the sidewall portions 28 for aesthetic and safety reasons. In addition, the sidewall portion extender 36 prevents items from falling off the back and sides of the table top of the table unit 76. Optional sidewall portion extenders 80 are releasably connected to the sidewall portion 28 of the table unit 76 so that the multiple sidewall portion extenders 80 are stacked below the sidewall portion 28 of the table unit 76 to form table legs. Alternatively the intermediate wall boards 42 may be used to form the table legs, thus adding to the modularity of the reconfigurable modular furniture system. The number and arrangement of sidewall portion extenders 80 or intermediate wall boards 42 may vary depending on the desired appearance and/or height of the table unit 76. It will be appreciated that the multiple sidewall portion extenders 80 may be replaced by a single sidewall portion extender 80. The table and seat unit 74 includes optional base portion support structures 82. The base portion support structures 82 are releasably connected to the base portion 26 of the seat unit 78 so that the base portion support structures 82 are stacked on top of each other and below the base portion 26 of the seat unit 78. In this way the base portion support structures 82 form a base underneath the sitting surface. The number and arrangement of base portion support structures 82 may vary depending on the desired appearance and/or height of the seat unit 78. It will be appreciated that the multiple base portion support structures 82 may be replaced by a single base portion support structure 82. The connections may be achieved using cam dowel fasteners inserted in holes 34 in the connected parts and securing them using cam locks. When forming the table and seat unit 74, either or both of the base portions 26 may require detachment from the sidewall portions 28, turning over and reattachment to the sidewall portions 28 in order to hide fastener features (e.g. fastener holes) on one side of the base portions 26. Figure 1g and 11 show a seat unit 84 which is used by the child for sitting. The seat unit of Figure 1g and 11 is taller than the seat unit 84 of Figures 1f, 9 and 10. To form the seat unit 84, the first and second furniture components 22,24 are stacked on top of each other. The lower furniture component 22 is turned upside-down so that the base portions 26 of the lower and higher furniture components 22,24 can be releasably connected to each other. The lower furniture component 22 is supported on the ground by an optional sidewall portion extender 36 releasably connected to its sidewall portion 28. Another optional sidewall portion extender 38 is releasably connected to the sidewall portion 28 of the higher furniture component 24. The connections may be achieved using cam dowel fasteners inserted in holes 34 in the connected parts and securing them using cam locks. In this way the first and second furniture components 22,24 form the seat unit 84 in which the base portions 26 of the first and second furniture components 22,24 are stacked on top of each other to form a sitting surface of the seat unit 84. The sidewall portion 28 of the higher furniture component 24 forms a seat back and seat armrests while the sidewall portion 28 of the lower furniture component 22 forms a base underneath the sitting surface. When forming the seat unit 84, either or both of the base portions 26 may require detachment from the sidewall portions 28, turning over and reattachment to the sidewall portions 28 in order to hide fastener features (e.g. fastener holes) on one side of the base portions 26. A reconfigurable modular furniture system according to a second embodiment of the invention is shown in Figure 12. The reconfigurable modular furniture system of Figure 12 is similar in structure and function to the reconfigurable modular furniture system of Figure 1, except that the reconfigurable modular furniture system of Figure 12 is designed to be transformable into the baby crib 20, the shelf unit 72 and the seat unit 84, and optionally the cart 68. This embodiment may further include four caster wheels 50 to permit optional transformation into the cart 68. A reconfigurable modular furniture system according to a third embodiment of the invention is shown in Figure 13. The reconfigurable modular furniture system of Figure 13 is similar in structure and function to the reconfigurable modular furniture system of Figure 1, except that the reconfigurable modular furniture system of Figure 12 is designed to be transformable into the cot 58, the table and seat unit 74, the shelf unit 72 and the seat unit 84, with the mat 52 being usable on its own as an activity mat. The embodiments of Figures 12 and 13 provide reconfigurable modular furniture systems that are transformable to a fewer number of furniture units and requires a fewer number of parts in comparison to the embodiment of Figure 1. This may be suitable for users who only need a smaller range of furniture units or who have a smaller spending budget. A reconfigurable modular furniture system according to a fourth embodiment of the invention is shown in Figures 14 to 17. The reconfigurable modular furniture system of Figures 14 to 17 is similar in structure and function to the reconfigurable modular furniture system of Figure 1, except that the reconfigurable modular furniture system of Figures 14 to 17 is designed to be transformable into a cot 86, the table and seat unit 74, the shelf unit 72 and the seat unit 84. In this embodiment, the reconfigurable modular furniture system further includes two additional sidewall portions 88 and a rigid floor component 90. The rigid floor component 90 may be a wooden floor component. When the reconfigurable modular furniture system is transformed into the cot 86, the additional sidewall portions 88 are releasably attached (e.g. using cam dowel fasteners and cam locks) between the sidewall portions 28 of the first and second furniture components 22,24, so that the sidewall portions 28 and the additional sidewall portions 88 form a continuous wall, with the first and second furniture components 22,24 facing each other and having a gap therebetween. Optional intermediate planar sidewall portion extenders 66 may be stacked on top of the additional sidewall portions 88. The number of sidewall portion extenders 66 may vary depending on the desired height of the wall of the cot 86. The rigid floor component 90 is releasably attached (e.g. using Allen screws) to the base portions 26 of the first and second furniture components 22,24 within the continuous wall, so that the rigid floor component 90 bridges the gap between the first and second furniture components 22,24. In this way the base portions 26 and the rigid floor component 90 form the floor of the cot 86. The provision of the additional sidewall portions 88 and the rigid floor component 90 allows the formation of a longer cot 86 (e.g. 1.2m long) using the reconfigurable modular furniture system of the invention. It will be appreciated that, in embodiments of the invention, each furniture unit may be transformed into any one of the other furniture units. That is to say, the transformation from one furniture unit into another furniture unit is not limited to the above-described transformation sequences. It is envisaged that, in other embodiments of the invention, a playpen unit may be formed by connecting the first and second furniture components together and omitting the wheels and support legs. It is envisaged that, in other embodiments of the invention, other types of fasteners may be used in addition or in place of the cam dowel fasteners. The listing or discussion of an apparently prior-published document or apparently prior- published information in this specification should not necessarily be taken as an acknowledgement that the document or information is part of the state of the art or is common general knowledge. Preferences and options for a given aspect, feature or parameter of the invention should, unless the context indicates otherwise, be regarded as having been disclosed in combination with any and all preferences and options for all other aspects, features and parameters of the invention.