Brothers Otavio and Gustavo Gandolfo, best known as Os Gêmeos, started painting in 1987. Over the course of their career, the twins have helped define Brazil's graffiti style and build a firm global following. Through unique portraits (informed by traditional hip-hop graffiti and the Brazilian Pixação), Os Gêmeos comment on social ills in truly colorful fashion.

As international muralist, Os Gêmeos have covered the walls of buildings from Berlin to Portgual (and the walls of museums and galleries from Brazil to New York City). They've even painted a castle in Scotland. In each instance, the brother's create evocative, if familiar, work that never fails to capture the attention of folks strolling past.

Click on for the best of Os Gêmeos.