 This review discusses the use of pharmaceutical and cosmetic topical products containing polymeric nanoparticles, such as nanospheres and nanocapsules, for drug delivery through the skin. The extent of penetration and transport depends on various factors including ingredient composition, encapsulation mechanism, particle size, and formulation viscosity. These nanoparticles can modify drug activity, control release, increase adhesivity, and prolong time in the skin, making them useful as reservoirs for lipophilic drugs to enhance permeation into the skin. This article was authored by Silvia Escuterres, Marta P. Alves, and Adriana R. Paulman.