Although microbes were first observed over three hundred years ago, the field of microbiology can be said to be in its infancy relative to older biological disciplines such as zoology and botany. Microbiology could be defined as the study of microorganisms, which are unicellular or cell-cluster micro-scopic organisms. Whilst there are undoubtedly some who fear all microbes due to the association of some microbes with many human illnesses, many microbes are also responsible for many beneficial processes such as industrial ferme-ntation, antibiotic production and as vehicles for cloning in higher organisms such as plants. The present book has been designed to outline the basic aspects of microbiology to be understood in its right perspective. It envisages to put forward a clear understanding of what is microbiology and its widening horizons. It is designed for students taking courses various fields of life sciences.