The proposed book was written by a classic of domestic science, one of the leaders of the Soviet nuclear program, academician I . B. Zeldovich in the last period of his work together with two - then still young - co-authors of A. A. Ruzmaykin and D. D. Sokolov . The book was first published in English by Gordon and Breach in 1983. The authors introduce here a number of new concepts of electrodynamics and magnetic hydrodynamics of space environments. Specifically , give an idea of fast dynamo and topological interpretation of conditions of fast generation of magnetic field , Consider the formation of magnetic fields in spiral galaxies and in the convective shells of stars. Together with other monographs published during this period, the book formed the modern paradigm of studying magnetic fields in space. Over the years, it has not lost its relevance, is widely cited in the scientific literature, is represented in almost all foreign libraries of astronomical profile. However, until now, this book has remained practically inaccessible to the domestic reader.