The book introduces the reader to the fascinating science of substance transformations. The simplicity of the presentation of the material does not require a high level of training from the reader in the field of mathematics, chemistry and thermodynamics. Enough knowledge of the basics of these sciences. The publication includes three parts, respectively, on empirical kinetics, the elementary theory of one-step reactions, the kinetics of complex cyclic processes (chain and catalytic), as well as on the kinetics of reactions in complex systems. Such systems are natural systems: atmosphere, water, soil and living organisms.