The reduced dimensions of magnetic thin films and nanostructures lead to major and often unexpected changes in magnetic properties and behavior. In addition to intrinsic scientific importance, these novel characteristics have obvious relevance to current and projected technological needs. Successful implementation of this technology requires a detailed understanding of materials growth mechanisms. Chemical and crystallographic structure must be correlated with micromagnetic structure and dynamic response before the fundamental limits of device performance can be firmly established. For example, atomic-level imaging and microanalysis of structural and chemical changes induced by changes in growth temperature or by post-deposition annealing are essential for explaining enhanced magnetic properties of antiferromagnetic pinning layers and magnetic tunnel junctions. And electron holography allows direct visualization of magnetization behavior within patterned nanostructures. This talk will provide an overview of electron microscopy and related techniques, with illustrative examples that demonstrate the major contributions being made to ongoing studies of magnetic thin films and nanostructures.