Molecubes

Molecubes are a collection of modular robots created by Hod Lipson and Victor Zykov from Cornell University. A molecube is made of two rotatable halves, one with the microprocessor which represents the intelligence behind the unit, and the other with a motor for rotating the joint. A group of the cubes can be connected into a variety of shapes.
A robot constructed entirely of molecubes would be able to repair itself using extra cubes, and to create a copy of itself using the same number of cubes.