The monograph systematically presents the theory of electron and positron radiation and the birth of a pair of photons in oriented single crystals. A general theory has been developed that is applicable at any energies and angles of entry of the initial particle into the crystal. In addition, the processes of radiation during channeling, the generation of pairs by a charged particle, the splitting of a photon, the generation of neutrino pairs by an electron, as well as the forced emission of charged particles during their movement in crystals are considered.