The statistical mechanics of systems not in thermal equilibrium. One of the main purposes of nonequilibrium statistical mechanics is to calculate transport coefficients and inverse transport coefficients, such as conductivity and viscosity, from first principles and to provide a basis for transport theory. The nonequilibrium systems easiest to understand are those near thermal equilibrium. For systems far from equilibrium, such possibilities as chaos, turbulence, and self-organization can arise due to nonlinearity.