 Polymeric nanoparticles have been used for decades to improve the delivery of drugs and cosmetics through the skin. These particles can be designed to release drugs slowly, allowing for more effective treatment with fewer side effects. They can also be used to enhance the absorption of active ingredients into the skin, resulting in better results from cosmetic treatments. This article was authored by Silvia Escuteras, Marta P. Alves, and Adriana R. Paulman.