Thin films adsorbed on solid substrates frequently exhibit properties which are quite distinct from those exhibited by the bulk material. As such two-dimensional films thicken, they must eventually exhibit three-dimensional behavior. Current research is focused on various aspects of this evolution from two- dimensional to three dimensional behavior as a film grows: Employing model systems of rare-gas films on well characterized substrates, two fundamental issues of film growth are addressed: (1) Given a known substrate and a known adsorbate, can one, based on atomistic principles alone, predict the mode of growth which will occur? (2) How can one alter a particular film substrate combination so as to obtain a desired mode of film growth? The overall goal here is to decrease our reliance on empirical approaches to the characterization and prediction of film growth modes and to bridge the gap between "ideal" and "real" surfaces. Other research interests include studies of the relationship between film surface melting characteristics and wetting behavior, and the preparation of metal substrates by ballistic aggregation allowing adsorption studies on fractal and/or void networks.