Design and implementation of HexBot: a modular self-reconfigurable robotic system. This paper proposes the design and implementation of a planar hexagonal Modular Self-Reconfigurable Robotic System (MSRRS). A universal module is carefully designed to reflect the primary required criteria such as homogeneity, cost-effectiveness, fast actuation, and quick strong connections. While our working prototype is both large and restricted to a planar motion, it is designed so that the hardware and software can be scaled up in the number of units and down in unit size and it can be extended to accommodate 3D applications. One of the novel approaches in our design is that it is based on a multilayer approach where each layer is dedicated to perform a specific task; in other words, the design itself is considered to be modular. This multilayer approach in both the hardware and the software enables each layer to be modified and enhanced while keeping the remaining layers untouched, providing openness, flexibility, and ease of modification. The software infrastructure of this system is designed to allow the implementation of different hierarchies for distributed control and communication.