This lecture covers the significance of microbiology in the practical activity of doctors, the history of microbiology, and the classification and structure of microorganisms. Microbiology is a science that studies the most shallow living creatures, microorganisms. Before the invention of the microscope, humanity was unaware of their existence. However, over the centuries, people have been able to harness the vital processes of microbes for various needs, such as preparing koumiss, alcohol, wine, vinegar, bread, and other products. The nature of fermentations remained incomprehensible for many centuries.