Years ago, critics of graffiti and street music were fusing. But today, who has never seen a report on Banksy on the news, photographed the mosaics of Invader at the corner of a street, cracked for a t-shirt or cap "Obey" or just wanted to see more of colors on the gray walls of his city? This book examines the role of public and private actors in this growing popularity of urban art; the artistic movement of the 21st century?