This interdisciplinary journal is devoted to the physics, chemistry and materials science of diffusion, mass transport, and reactivity of solids. The major part of each issue is devoted to articles on:(i) physics and chemistry of defects in solids;(ii) reactions in and on solids, e.g. intercalation, corrosion, oxidation, sintering;(iii) ion transport measurements, mechanisms and theory;(iv) solid state electrochemistry;(v) ionically-electronically mixed conducting solids.Related technological applications are also included, provided their characteristics are interpreted in terms of the basic solid state properties.Review papers and relevant symposium proceedings are welcome.