  The review presents basic elements of the theory of electromagnetic emission
by nonthermal particles propagating in stochastic media. In particular, general
theory and a few special regimes of Diffusive Synchrotron Radiation
(DSR)arising in the presence of random magnetic/electric fields are analyzed in
detail. Possible applications of the DSR theory to astrophysical sources as
well as other emission processes typical for the random media are discussed
briefly.
