In the last few decades, street art has transformed from a mostly illegal medium used by artists in urban environments to a global art movement of sought-after pieces earning millions at art auctions. We discuss this and more with Blek le Rat, the world's most famous Parisian street artist and father of the art form's stencil-based technique, and Brian Greif, an art collector showing Banksy's San Francisco piece "Haight Street Rat" in Waco and around the world.