A modular controller expansion kit is a small hub board. It plugs into a classroom microcontroller and adds more sensor ports, motor channels, and power inputs. A board like the Bit Base Robotics Kit works well as a starting point, since it already supports several expansion options.Once a class outgrows the base setup, the expansion hub becomes the next step. It doesn't replace the original board. It just gives that board more room to grow. That's the whole idea behind modular expansion. Teache