This paper is the first review devoted to the localized‐particles approach for strongly anharmonic crystals. We present mathematical basises of such an approach for classical and quantum cases and we discuss its different applications. In the framework of this method various technical tricks and detailes could, of course, be changed, but the main idea should be conserved: that of the localization of atoms, forming a solid, near their lattice sites. The localized‐particles approach describes not only collective excitations as the phonons but the state of particles themselves too; that is why it is much more convenient for describing crystals with defects, crystal‐gas intersurfaces, disordered solids and some phase transitions. Copyright © 1983 WILEY‐VCH Verlag GmbH & Co. KGaA