As interest in theoretical biology grows, so does the need for an accessible link between these theories and experiments. The central purpose of this book is to illustrate the premise that examination of the kinetics of biological processes can give valuable information concerning the underlying mechanisms that are responsible for these processes. Topics covered range from co-operativity in protein binding, through receptor-infector coupling, to theories of biochemical oscillations in yeast and slime mould. In addition, an introduction to the explosively growing theoretical topic of chaos details attempts to apply this theory in physiology. The material of this book originally appeared as part of the volume Mathematical Models in Molecular and Cellular Biology (edited by L. A. Segel). However each article has been revised and updated.