The unique attributes of a Field Ion Microscope-(FIM) permit direct observation of the surface diffusion of a single atom and simple atomic clusters on perfect crystal planes. A brief review of the principles and techniques of such studies is presented along with a collection of existing experimental data. Included is a one and two dimensional random walk of a single adatom or di-atomic cluster on well defined crystal planes, the structure and configuration of an atomic cluster on crystal surfaces, the experimental demonstration of non-monotonic long-range interaction obtained from the distribution functionof the distance between two adatoms on a single-crystal surface, and an atomic view of surface self-diffusion of clean and well defined surfaces.