Book excerpt: ^Energy and Life addresses the subject of energy in biological systems. It concentrates on the way in which energy flow through plants, animals and bacteria drives the primary processes of life such as metabolism, movement and ion transport. It deals with living systems from a whole-body approach, for exampke in starvation and obesity, to the cellular and molecular level where modern advances in biochemistry and molecular biology are revolutionising our knowledge of how "molecular machines" work. Extensive illustrations, concept boxes, summary sections, suggested further reading lists, as well as questions and answers aid with the presentation of a sometimes daunting, yet fascinating, area of biological science.