We present an overview of the critical issues of current interest in magnetic and magnetoelectronic materials. A broad demonstration of the successful blend of materials synthesis, microstructural evolution and control, new physics and novel applications that is central to research in this field is presented. The critical role of size, especially at the nanometer length scale, dimensionality, as it pertains to thin films and interfaces, and the overall microstructure, in determining a range of fundamental properties and potential applications, is emphasized. Even though the article is broad in scope, examples are drawn mainly from our recent work in magnetic nanoparticles and core-shell structures, exchange, proximity and interface effects in thin film heterostructures, and dilute magnetic dielectrics, a new class of materials for spin electronics applications. (c) 2006 Springer Science + Business Media, Inc.