This article reviews that status of POSS for use in adhesive systems, primarily epoxy and polyurethane, although POSS has found advantages in other systems as well. The unique physical properties of POSS are described and an explanation is given as to how it affects bulk and adhesive properties. The various types and functionalities of POSS products are identified and related to adhesive systems. Polyhedral-oligomeric-silsesquioxane (POSS) is a unique kind of inorganic silica particle that has become one of the first nanomaterials to be commercialized for use in polymeric systems. The incorporation of POSS into polymeric networks has been found to result in dramatic improvement in properties. Generally, POSS additives can be used as a multifunctional additive, acting simultaneously as molecular level reinforcement, processing aid, and flame retardant. The unique characteristics of POSS provides for a diverse range of nanostructured products including thermosets, thermoplastics, and composite materials.