Microbiology is the study of micro-organism, of microbes, a diverse group of generally minute, simple life-form that include bacteria, archaea, algae protozoa and viruses. The field is concerned with the structure function and classification of such organisms and with ways of both exploiting and controlling their activities. This is the collection of many science viz. Botany, Zoology, Genetics, Environmental Science, Biotechnology etc. Microbiology deals with all these field and applied all of its application. Daily life is inter-women inextricably with micro-organisms, in addition to populating both the inner and outer surface of the human body microbes around in the soil in the seas and in the air abundant although usually unnoticed micro-organisms provide ample evidence of their presence sometimes unfavorably as when they cause decay of materials or spread diseases and sometimes favorably as when they ferment sugar to wine and beer, cause bread to rise flavor cheeses and produce valued products such as antibiotics and insulin. Micro-organisms are of incalculable value to Earth’s ecology in the other organisms. The books covers the basics of microbiology starting with a brief history of microbiology and the impact microbes metabolism to provide a background on the function of microbes before delving into their in diseases and heath. The various cycle viz. carbon and nitrogen cycle is described in various steps. Denitrification, nitrification and nitrogen fixation. Stages of nitrogen Fixation are being discussed in details. This book dealt with microbial classification, industrial and biotechnological application. The book aim to educate the graduates with the basic knowledge of micro-organism starting from the structure of Bacteria, virus and fungi with clears figures and pictures and ending with their application in various field. This book will be helpful for the students pursuing graduates and also preparing themselves for the various competitive examinations. Contents: History of Microbiology Branches of Microbiology Applications of Microbiology Structure of Bacteria, Their Parts and Functions Microscopy and Specimen Preparation Classification, Nomenclature and Identification Bacterial Growth Bacterial Genetics DNA Replication, Transcription, Translation Bacterial Recombination Introduction to Fungi and its Classification Structure of Virus and its Classification Soil Microbiology Microbiology of Water Microbiology of Sewage Treatment Microbiology of Air Enumeration and Control of Airborne Micro-organism Food Microbiology Industrial Microbiology and Biotechnology Micro-organism in molecular Biology Safety in Microbiology Methods (Laboratory Rules) Some Milestone in the Field of Microbiology and Biotechnology References