The monograph written by Mihoko Otake combines ideas from chemistry and physics, material science and engineering for the revolutionary development of the so-called gel robots. Electroactive polymers are introduced to build new types of muscular-like actuation for deformable robots. The coverage spans from modelling and design to the development, control and experimental testing. A number of methods are proposed for describing the shapes and motions of such systems. The results are demonstrated for beam-shaped gels curling around an object and starfish-shaped gel robots turning over.