Plasma polymerization leads to polymer film formation at low temperatures, e.g. at room temperature, on any substrate. It is one of relatively few processes which permits the formation of very thin uniform polymer films which conform to a substrate of any shape. In general, such films are amorphous throughout, using electron diffraction as a criterion. By appropriate control of the rate limiting plasma processes the structure of the polymer can be modified at will. So, for example, the degree of cross-linking and resultant chemical and physical properties can be manipulated over a wide range. Work in this laboratory has specialized in a unique process which permits uniform matrix isolation of a variety of materials, such as for example zero valent metal clusters, throughout the polymer matrix. The volume fraction and size of such clusters within the matrix can be readily controlled. Clearly, a variety of properties of such a composite system can be changed in a systematic way. Emission spectroscopy as well as mass spectrometry provide convenient means of monitoring some of the key processes occurring in the plasma. Solid state N.M.R., E.S.C.A., I.R., T.G.A., and D.T.A. and electron microscopy and diffraction serve to characterize the structure of the films.