Lokiss is one of the pioneers in the European graffiti culture, as well as one of the main contemporary street artists. Under his direction, a new book aims to recount the history of modern graffiti, aka writing, from 1970s New York metro to today walls and institutions. "50 Years Of Urban Interactions" study the signs and the language, approaching in a conjoint way the artistic element and their contextual continuation. This volume analyses the convergence of the problematics of art and its integration in the social and political sphere, in a culture initially based on illegality. It sheds light on the historic interaction between street and art, between vandalism of the public good and the museum of the cultural object.