Since the early 1990s, the subject of polymer nanocomposites has expanded greatly, to its current status as a major field of polymer materials research. It is now realized that polymer nanocomposites, as a class of materials, were in use long before this field of research was officially named in the early 1990s. Indeed, work published as early as 1961, and patents going back to the 1940s, have shown that layered silicates (or clays) can be combined with polymers in low amounts to produce new materials with greatly improved properties. However, it was the work in the 1990s that properly identified these clay-containing materials as polymer nanocomposites and kindled today’s interest in these materials. One could argue that polymer nanocomposites are just part of the nanotechnology boom, but there is more to it. The fundamental understanding of how two dissimilar materials interface at the nanometer scale has tremendous implications for performance and properties at the macro scale. Therefore, the study of polymer nanocomposites is not just about capturing the buzz from nanotechnology; it is about understanding structure–property relationships and interfacial science at the molecular and macromolecular scale