Microbiology is the science of microorganisms, which are living beings invisible to the naked eye including bacteria, fungi, protozoa, algae and viruses. Microbiology is one of the fields of biological sciences, which is devoted to the identification and characterization of microbes, to the study of their origin and evolution, to define their characteristics and the products of their activities and their needs. This course provides basic information on the world of microorganisms in five chapters, ending with review questions. This book is a scientific and pedagogical support that helps the student to assimilate and learn the maximum amount of information required.