It is now well accepted that microbial life followed very quickly after the formation of liquid water on the early earth, and that for the next 3,000 million years life was a unicellular phenomenon. During this immense period of time all the major types of microbes appeared, as did all the fundamental chemical pathways necessary for life. This diversification was not well appreciated until the techniques of molecular biology provided a means to examine the relationships between microorganisms which share few, if any, phenotypic characters. This volume reviews the current understanding of the evolution of microbial life during that time. The chapters draw together the various threads of the story to uncover what has been learned about the process of evolution itself and what this knowledge can contribute to the understanding of biodiversity.Available at discount to members of the Society of General Microbiology - Please contact the society for details.