21st century is an exciting time for microbiology, especially post COVID-19 pandemic. We are becoming increasingly aware that microorganisms are the basis of the biosphere and are relevant to all our lives in a multitude of ways. Third edition of the book "A Textbook of Basic and Applied Microbiology" provides up-to-date information of all aspects of microbes-fundamental, applied and causative agents of human diseases. The book is well-designed and well-written in a simple language understandable to readers of diverse backgrounds at the undergraduate and postgraduate level, and will serve as an important tool to qualify ICAR, UGC and CSIR NET examinations. The book is divided into three sections: Basic, Applied and Medical Microbiology. The Basic Microbiology section covers chapters on fundamental aspects of microbiology such as historical milestones in microbiology, microbial taxonomy, structure, physiology, biochemistry, genetics, molecular biology, and physical and chemical control of microorganisms including principles of antimicrobial chemotherapy. The Applied Microbiology section lays emphasis on the diverse applications of microorganisms in industry, health, environment and agriculture and includes chapters on soil, air and water microbiology, food and environmental microbiology, industrial microbiology and biotechnology and a fascinating field of exobiology highlighting discovery of microbes in outer space. The Medical Microbiology section includes important chapters on fundamentals of immunology and microbial pathogenesis, various infectious diseases caused by bacteria, fungi, viruses and parasites in humans which include mycoses, skin, eye and ear diseases, oral and dental diseases, upper and lower respiratory tract diseases, gastrointestinal diseases, urogenital and sexually transmitted diseases, systemic and nervous system diseases and a chapter on diagnostic microbiology which deals with the techniques used by a clinical microbiologist to isolate and identify the pathogenic microorganism in a clinical specimen.