Microorganisms are a group of organisms that are characterized with the quality of being visible only with the help of a microscope. This book unveils new topics revealing the scale of genetic diversity of microorganisms existing in various environmental circumstances. The complexity and variety of microbial populations is by far the uppermost among all living organisms. The variety of microbial communities and their ecologic roles are being constantly analyzed in soil, water, plants and animals, and in tremendous environments such as the arctic deep-sea vents or high saline lakes. The growing accessibility of PCR-based molecular developers allows thorough researches and valuation of genetic range in microorganisms. The motive of the book is to offer a glance into the dynamic procedures of genetic diversity of microorganisms by providing the views of experts who are involved in creation of bright ideas and methods employed for the assessment of genetic diversity, often from different perspectives. This book should be helpful to amateurs and experts in the field of molecular biology.