Archaea is a very old group of prokaryotic microorganisms distinguished by unique characteristics from other procaryotic representatives. Archaea represent the third discrete domain of life. The recent research focused on biology and ecology of Archaea has brought quite new and fascinating information about these microorganisms as well as about the life evolution in general. By virtue of application of recent molecular methods, it is apparent that archaeal habitat is not limited only to extreme environments but it is a distributed group coexisting with other microorganisms in common environments. The study of archaeal role in processes of C and N transformation connected with production and emission of greenhouse gases belongs to important problematic of recent soil biology. From a point of view of the evolutionary relations among soil organisms or interaction with other representatives of edafon the study of Archaea represents other important tasks of soil biology.