  Collective phenomena in strongly nonequilibrium systems interacting with
electromagnetic field are considered. Such systems are described by complicated
nonlinear differential or integro-differential equations. The aim of this
review is to show that many nonlinear collective phenomena can be successfully
treated by a recently developed method called the Scale Separation Approach
whose name is due to the idea of separating different characteristic space-time
scales existing in nonequilibrium statistical systems. This approach is rather
general and can be applied to various nonequilibrium physical problems, several
of which are discussed here. The problems considered not only serve as
illustrations of the method but are quite important by themselves presenting
interesting physical effects, such as Collective Liberation of Light, Turbulent
Photon Filamentation, Superradiant Spin Relaxation, Negative Electric Current,
and Magnetic Semiconfinement of Atoms.
