The fringe is the contemporary city “in-between space”, in which urban and periurban features interweave. In European cities, this transitional belt often matches with the Post World War II expansion. Nowadays, the urban fringe, generally in decline, offers huge chances for regeneration. For this aim, innovative planning tools are required, more flexible and adaptive than the traditional blue-print based. The book collects the ongoing experiments focused on innovative planning modes, carried out in some European cities within the Urbact III network “Sub>urban. Reinventing the fringe”.