This book correlates the vast genetic diversity associated with environmental samples and still underexploited potential for the development of biotechnology products. The book points out the potential of different types of environmental samples. It presents the main characteristics of microbial diversity, the main approaches used for molecular characterization of the diversity, and practical examples of application of the exploration of the microbial diversity. It presents a not-yet-explored structure for discussing the main topics related to molecular biology of environmental prokaryotes and their biotechnological applications.