The first research on plasma was done in connection with the study of electrical discharges in gases. The focus of attention for physicists was the partially ionized plasma, the kinetics of which is governed by various collisional and radiative processes. The choice of this area of research was motivated largely by the practical problems of that time the creation of gas-discharge light sources, rectifiers, and inverters. Since the early 1950s interest in plasma physics has risen sharply, particularly in the study of the completely ionized plasma with its various collective phenomena, insta­ bilities, and the interesting and sometimes unexpected effects attending the propagation of electromagnetic waves in such a plasma and the action on it of external electric and magnetic fields. Interest in hot plasmas has been stimulated not only by the diverse and novel physical phenomena, but also by the problems arising in connection with controlled nuclear fusion. The advent, in the early 1960s, of new technical fields such as gas-discharge lasers, magnetohydrodynamic generators, thermoemission converters, plasma chemistry, plasma propul­ sion devices, various methods in plasma technology, etc. , has led to increased interest in weakly ionized low-tempera­ ture plasmas. This is particularly true of nonequilibrium plasmas, which are characterized by an extraordinary diver­ sity of states and properties.