Summary of the results of studies of the internal structure of the Earth. It is distinguished by a rare combination of encyclopedic and high scientific level of presentation. The book examines the physical and chemical models of the Earth, comprehensively analyzes the hypotheses of the origin and structure of the Earth and the Moon. Especially interesting are new experimental data on the chemical and mineral composition of the core, lower and upper mantle, theoretical generalizations regarding the evolution of the Earth's magnetic field, an analysis of the features of the formation of the Earth's crust and the emergence of ocean basins from the standpoint of plate tectonics, etc.