This anthology is devoted to the theoretical and experimental study of coherent phenomena in quantum optics. Considerable attention is devoted to the investigation of cooperative effects in multilevel molecular and atomic systems. The theoretical analysis is based on a single approach, using the theory of groups, which makes it possible to present the results in a compact and physically elegant form. The results of a detailed experimental and theoretical investigation of the photon echo, self-induced transparency, and nutation are presented. The theory of a coherent resonant mechanism for the interaction of laser radiation with multi­ atomic molecules which causes "prompt" dissociation is presented. A number of applied pos­ sibilities, in particular, the control of radiation by laser light and laser isotope separation, are analyzed.