Scanning tunneling microscopy, first developed by G.Binnig, H.Rohrer, Ch.Gerber, and E.Weibel [1] in 1982 as a method of directly observing atom sites at the surface of graphite and other crystalline materials, is now being used in an ever increasing variety of applications as a result of steady and rapid advances in instrumentation, interpretation, and specimen handling techniques [2]. As a result the STM is widely recognized as a powerful method of observing surface structure on an atomic scale and is fast becoming an accessory tool in materials characterization laboratories that are devoted to solving industrial problems. Some examples representative materials characterization studies are described in mis paper.The first STM studies employed its high resolution capabilities for fundamental studies of the topography of atoms at surfaces [2]. More recently the value of the STM to observe both surface topography and electronic structure has been utilized. Figure 1 is a STM image of a charge density wave (CDW) from a TaS3 sample at 143K[3]. In this work the advantage of STM, due to sensitivity to both surface topography and electron structure, is apparent.The development of long scan STMs with scan capabilities of several micrometers or more has opened up a whole new class of materials where the magnifications required are comparable to that of a conventional SEM. The 3-dimensional structure of a processed optical recording disk, as revealed by the STM, is illustrated in Figure 2. The ability of the STM to observe both the course and ultrafine structure of such a sample makes it a powerful tool for relating processing conditions to surface structure defects and hence to the quality and reliability of the optical storage disk itself.