For four decades, street art has not failed to break the codes and arouse the interest of an ever-growing audience. From Miami to Shanghai via London and Berlin, hordes of tourists and photographers are interested in frescoes and graffiti on the walls, and Paris, with a unique historical scene, stands out as one of the capitals of this movement. Paradoxically, and despite the literature provided on this subject, no one seems to be trying to understand what led to the fact that, suddenly, artists began to place art on the street, illegally and free of charge. However, street art is a pure product of our society, and constitutes a healthy and artistic reaction to a world that erects more and more barriers between the citizen and his freedom. It deserves more attention and questioning than the usual confusion maintained in the media between graffiti, street art and municipal art. This essay, in the form of a manifesto, attempts not to propose yet another historical chronology of urban art but to understand the reasons that have led women and men to invest savagely and artistically the walls, in order to identify the primordial asperities of which stands out as the major artistic movement of our time.