This book presents the various types of resonance effects on excitons, biexcitons and the local electronic centers (LEC) in solids, such as paramagnetic and paraelectric resonances on excitons, exciton acoustic resonance at intra- and interband transitions, radio-optical double resonance on excitons, hole-nuclear double resonance on localized biexcitons, ENDOR and acoustic ENDOR on LEC. The criteria for the generation of coherent photons, phonons and magnons by excitons are explained. The interactions of excitons and biexcitons with paramagnetic centers and nuclear spins, the indirect...