This brief introduces the structural and functional characterization of this important group of proteins. The content of each chapter is aimed at the non-specialist so that key concepts, methodologies and applications can be presented in a "snapshot" style volume. Multiheme cytochromes are ever more important now that it is possible to obtain genome sequences of microorganisms which have major biotechnological and environmental implications. There is a tremendous profusion of multiheme cytochromes which have great potential as targets for bioremediation and bioenergy applications. This brief gives a glimpse of an intriguing and fast-moving field.