The book tells about the history of the discovery of isotopes of chemical elements, the role of isotopes in the mastery of atomic energy, and the main methods for separating isotopes. Particular attention is paid to the history of the development of methods and industrial installations for the separation of uranium isotopes (both within the framework of the US Manhattan Project and the Soviet atomic project) in connection with materials discovered and published in recent years. A significant part of the book is devoted to a popular presentation of the physical foundations of molecular kinetic methods isotope separation. The author hopes that this will allow us to better understand what specific ideas and ideas were guided by scientists, technologists, designers and engineers who had to develop these methods and bring them to practical implementation. It was thanks to their efforts that a modern separation industry for the production of isotopes was created in our country and a number of other developed countries of the world, which represents a truly new high-tech technology of the 21st century. The popular science publication is intended for teachers, high school students and lyceums with a technical focus , as well as first-year students of technical universities interested in the development of nuclear science and technology. The book may also be useful as an initial guide for students studying in the specialty “Physics of Kinetic Phenomena.”