A modular furniture building block for providing a modular furniture unit that can be combined with other units to construct or reconstruct any piece of furniture or structure. The modular furniture building block generally includes modular block panels that have a plurality of slots on the surface and/or sides and a plurality of cartridges to connect multiple block panels together at their slots. Multi-port receivers may be attached to the slots and the block panels may be connected by the cartridges via the multi-port receivers.