 This review discusses the use of pharmaceutical and cosmetic topical products containing polymeric nanoparticles, which can modify drug activity, delay and control release, increase adhesivity, and improve time of permanence in the skin, making them useful as reservoirs for lipophilic drugs to control their permeation into the skin. This article was authored by Silvia Escuteres, Marta P. Alves, and Adriana R. Polman.