For over three decades supersonic molecular beams have been used as tools in fields such as rarefied gas dynamics, spectroscopy and chemical reaction dynamics. Over the past several years we have been employing supersonic molecular beam techniques to investigate the fundamental aspects of Si and Si@sub 1-x@Ge@sub x@ thin film growth from gaseous precursors, and more recently to study the nucleation of Cu on SiO@sub 2@, TiN and TaN surfaces. These beams prove useful in our case due primarily to two factors- their (kinetic) energy tunability, and their high spatial and temporal resolution. This work using molecular beams has been combined with in situ surface sensitive analytical techniques, such as x-ray photoelectron spectroscopy, low-energy ion scattering and low-energy electron diffraction. We have also made use of independent sources of energetic species, in particular atomic sources, to examine cooperative and synergistic effects in thin film growth. The overall emphasis has been on both developing a better fundamental understanding of existing processes, and potentially developing new processes. We will present a brief overview of our work, focusing on investigations of the effects of strain on gas-surface reactivity in Si@sub 1-x@Ge@sub x@ epitaxial alloys; the growth of thin films at grazing angles of incidence; the exploration of scale-up strategies (experiment and computer simulation) for deposition over large areas, the use of atomic hydrogen to promote the selective area growth of epitaxial Si (and Si@sub 1-x@Ge@sub x@) on patterned Si-SiO@sub 2@ substrates, and the nucleation and growth of Cu on TiN and TaN barrier layers, and poly-Si on three-component (Ca-Al-Si)-oxide glasses.