Enzymatic biofuel cells, in contrast to conventional energy systems, use enzymes as catalysts for the conversion of chemical energy into electrical energy. These enzymes can also catalyze fuels such as sucrose, fructose and glucose. In addition to their use as catalysts, they are biocompatible in nature. Due to this fact, enzymatic biofuel cells have many interesting applications, such as implantable gadgets (biosensors, pacemakers, catheters, defibrillators, insulin pumps, self-controlled artificial muscles etc.). The book presents various aspects of biofuel cells including fuel cell electrochemistry, use of enzyme and enzyme immobilization techniques, use of materials such as mesoporous materials, graphene composites, conducting polymer composites and applications of biofuel cells.