ABSTRACT: In the large field of nanotechnology, polymer matrix based nanocomposites have become a prominent area of current research and development. Exfoliated clay-based nanocomposites have dominated thepolymer literature but there are a large number of other significant areas of current and emerging interest. This review will detail the technology involved with exfoliated clay-based nanocomposites and also include other important areas including barrier properties, flammability resistance, biomedical applications, lectrical/electronic/optoelectronic applications and fuel cell interests. The important question of the ‘‘nano-effect’’ of nanoparticle or fiber inclusion relative to their larger scale counterparts is addressed relative to crystallization and glass transition behavior. Of course, other polymer (and composite) based properties derive benefits from nanoscale filler or fiber addition and these are addressed.