Material support of all manned space flights so far has been provided from a prestored stock of substances or replenished from the Earth's biosphere. Exploration of space will, however, become real only when man is able to break away from Earth completely, when he will be accompanied by a system providing everything necessary to sustain full-valued life for an unlimited time. The only known system to date meeting this requirement is the Earth's biosphere. To break away from his cradle, as K.E. Tsiolkovsky called Earth, it is necessary to devise a life support system functionally similar to the natural biosphere. This need not be similar in structure to the vast diversity of trophic relationships available on Earth, but requires the solution of a multitude of various problems of an ecological, physiological, engineering and social-psychological nature. Human life-support systems based on biological regeneration of environments in small volumes have been studied at the Institute of Biophysics (Siberian Branch of the Russian Academy of Sciences) over many years. This work has resulted in the design of Bios-3, a biologically-based self-sustained human life support system.