This review article discusses humic substances - specific organic compounds, which are the substantial part of the bioenergy matrix of the food chains of living creatures and the essence of the exchange interaction of those media. The dead organisms (mostly plants) are transformed into humic substances. A prerequisite for creating the monograph was a steady interest in humic substances from humus specialists (soil scientists, agricultural chemists, coal chemists, etc.) and biologists, physicians, and workers in agriculture, forestry, and communal services. At the same time, monographs are quite rare in the literature, where humic substances are described quite fully. Based on our experience in studying humic substances, we have attempted to characterize humic substances comprehensively. Collecting disparate information and analyzing it made it possible to obtain a more or less holistic view of such a unique natural object as humic substances. Much attention is paid to the colloidal properties of these specific compounds. We must not forget that humic substances are a necessary and mandatory component of all metabolic processes in the biosphere.