microbial evolution and assess relationships of microbes in complex, natural c- munities. Recent developments in so-called ¿omics¿ technologies, including (meta) genomics and (meta)proteomics, and isotope labeling methods allow new insights into the function of microbial community members and their possible geological impact. While this book summarizes current knowledge in various areas, it also reveals unresolved questions that require future investigations. Information in these chapters enhances our fundamental knowledge of geomicrobiology that contributes to the exploitation of microbial functions in mineral and environmental biotechn- ogy applications. It is our hope that this book will stimulate interest in the general field of geomicrobiology and encourage others to explore microbial processes as applied to the Earth.