The book deals with one of the promising and interesting directions of laser physics - laser cooling of solids. The history of research in this direction is described briefly and the results of experiments with laser cooling of condensed media are discussed. Special attention is given to the physics of cooling processes and mathematical description of these processes. Problems of construction of self-cooling solid-state laser and echo-processors are investigated. One of the chapters is concerned with magnetic cooling, spin locking and photon locking, and also methods of reducing the uniform width of spectral lines of information carriers of optical echo-processors. Problems of optical cooling of solid-state quantum processors are also discussed.