The article contains a brief review of the basic works (1925-1981) written by Nikolay V. Timofeeff-Ressovsky--one of the famous geneticist of the elapsing century, the founder of radiobiology and radiation genetics, biocenology and radioecology, a prominent evolutionary biologist. In genetics, his name is associated with the development of fundamental problems of population genetics, phenogenetics, gene interaction and investigations of the role of environmental and genetic factors in expression of different characters. Timofeeff-Ressovsky classical works on mutagenesis process and especially, radiation mutagenesis, promoted penetration of methods and approaches applied in molecular physics and chemistry, into genetic analysis, and accelerated forming of the modern molecular genetics. A special place in the development of population genetics is occupied by the hypothesis of microevolutionary process developed by Nikolay V. Timofeeff-Ressovsky along with other famous biologists in the end of the 30-ies. This hypothesis connected Darwin's evolutionary theory with rapidly developing concepts of genetics. In the last years of his life, Timofeeff-Ressovsky was especially interested in a global problem which was called by him "The Biosphere and Humanity". Here was especially strikingly shown the broadness of his approach to the analysis of the biosphere phenomena in the best traditions of the Russian natural science. In the course of time, the wealth of Nikolay V. Timofeeff-Ressovsky's scientific heritage not only remains valuable, but also takes on more profundity and value.