First detailed study of the history of an art that has been created in the street for more than forty years and continues to change our experience of the city, Street art and graffiti portrays an artistic practice that does not resemble no other. In fact, what other art plays with the notion of illegality, dialogue with the built environment and questions so much the concept of public space? What other art is born so spontaneously and produces works whose authors know they are destined to disappear? We are here facing an unprecedented phenomenon, an exceptional current appeared outside the traditional frameworks that are the gallery, the museum or the art school. Giving the keys to understand the graffiti, its philosophy, techniques and vocabulary is all the more essential as this art, based on secrecy and anonymity, is not addressed to the general public a priori. Knowing his evolution makes it possible to understand how he opened the way to street art - an eminently protean practice that often combines contestation and poetry and is now part, like graffiti, of the art of our time. Banksy, Blek the Rat, Faile, Invader, Miss Van, Os Gemeos, Shepard Fairey or Swoon are some of the graffiti artists and street artists whose creations are analyzed in this remarkable work that addresses all the curious of visual culture contemporary.