Thin film materials pervade our everyday life as transparent conductors in LCD watches and computer displays and in defrosters for automobiles... antireflection coatings for camera lenses… optical fibers for communication … architectural glass coatings for both color and energy efficiency… solar cells… decorative coatings on plastics such as for toys and automobiles parts… a whole host of electronic and optoelectronic devices… hard coatings for cutting tools, drill bits, and bearings … even metallic coatings inside potato chip bags to keep the chips crisp!Without thin films our lifestyles would be drastically different. And this trend toward increased use of thin film technology will only continue.The varied reasons for using thin films and the specific deposition processes for preparing them are often complex; but usually relate to function, cost, beauty, materials and energy efficiency, and performance. In addition to technological applications, scientists are finding thin films to be an invaluable tool for investigating new physical phenomena, even at the quantum level. For instance, two of the most important new materials—high temperature ceramic superconductors and diamond coatings — are currently being made by several thin film deposition processes in order to explore both their scientific and technological potential.Just 25 years ago the variety of deposition processes for preparing thin films was quite limited. Thin film scientists and technologists had at their disposal electrodeposition, elementary chemical vapor deposition, evaporation, and dc sputtering. Commercial equipment for electron-beam evaporation, a mainstay in the optical coatings industry, was just being developed. Most of the deposition processes reviewed in this and next month's MRS BULLETIN were either not commercially available or were not even conceived of then.