The kinetics of microphase separation induced by the cure reaction of diglycidyl ether of bis-phenol A (DGEBA) was studied by NMR under isothermal conditions and in the presence of modifying agents. Polymerization and polycondensation mechanisms induced by diamine and tertiary amine systems respectively have been considered. Method of spin diffusion was shown to be useful for studying the microphase separation in curing polymer systems. The onset of microphase separation, phase composition, and size of heterophase inclusions were detected and/or characterized.