The fourth volume of Continuum Physics is devoted to the exposition of field theories for bodies which possess inner structure that can interact with mechanical and electromagnetic fields. The purpose here is a thorough and precise presentation of exact continuum theories on materially nonuniform or nonsimple bodies (bodies composed of single, dipolar, and deformable elements) that can respond to short- and long-range interparticle loads and fields. Most of these theories have acquired their present definitive forms during the last decade or so, even though basic ideas and certain limited or approximate developments on some of these theories can be traced back to the turn of the entury. With the explosive developments that have taken place during the last decade, continuum physics is now very rich, and the impossible dream of bridging the gap between classical phenomenological physics and atomic and molecular physics is in sight.