The special issue of the CMP journal Ferroelectricity and Multiferroics contains the papers of theoretical and experimental investigations in a wide range covering physical effects, properties and applications of ferroics–crystalline oxide, chalcogenide and hydrogen bonded materials with a long- range order parameter–spontaneous polarization, magnetization or strain. The order parameter arises due to the phase transition taking place with the temperature decrease, and at pressure or chemical composition variation. The phase transitions on the temperature–pressure–composition diagrams are investigated using different methods (first principles and model calculations, molecular dynamics simulations, mean-field analysis of thermodynamic properties) with the aim to search for the materials (monocrystals, ceramics and nanoparticles) having effective functional parameters, especially for multiferroics that have more than one of the interacting long-range orders. The fundamental physical research of nonlinear processes in ferroics on the nanoscale, with controlling the size effects, provides a background for developing nanostructures favourably applied in nanoelectronics and information technologies.