Characterization of submicrometer and subnanometer size particles is essential to understanding their interactions and to developing micro- and nanostructures. Because of this importance, marry advances and new developments have been made in characterization techniques for particles in this size range. Examples include neutron holography, in situ wet transmission electron microscopy, ultra-fast microscopy, magnetic resonance force microscopy for imaging a single electron spin, and high-resolution X-ray crystallography of noncrystalline structures. It is now possible to completely characterize very small particles from 0.1 nm to 100nm size. Selected recent developments are discussed.