Magnetic field effect on pyrene/N, N-dimethylaniline exciplex luminescence has been studied. Concept of un-relaxed (emitting at the blue end of the emission band) and relaxed exciplexes in polar solvents has been introduced. Bi-exponential decay of pyrene in condensed phase has been established which is explained on the basis of complex formation of excited pyrene with solvent molecules. The measurement of B1/2 values of the exciplex system in various neat and binary solvents throws light on the size of the transient, dielectric enriched micro-domains in binary solvents around the radical ion...