The tutorial introduces readers to the classification, sources, structural diversity, origin, biological role and applications of low molecular weight natural substances, which are secondary metabolites. It briefly addresses the fundamental issues of the chemistry of derivatives of higher fatty acids, isoprenoids, phenols, alkaloids, antibiotics, vitamins and other groups of natural compounds. In addition to the exclusively scientific interest in the knowledge of the chemical unity of life and the foundations of its functioning, the establishment of the structure and functions of secondary metabolites has wide areas of practical application, among which the most significant are medicine, ecology and directed chemical synthesis. The textbook is intended for chemistry students, as well as for undergraduates and graduate students specializing in fine organic synthesis.