Territories are objectively called to play a decisive role in designing and conducting the necessary transition. Whatever the subject, we discover that a city and a region are the best scale at which to approach the transition effectively. We also discover, however, that territories are not equipped, neither conceptually or institutionally, to assume these new responsibilities. A territory is a strong density, a hub of relations among actors internal and external to it, a crossroads of numerous flows of matter, information, energy, and persons. Emphasizing the need to define and reinforce the territory as actor does not in any way mean returning to the olden ages when territories were each practically self-sufficient. Today every territory has, much to the contrary, its stakes in a globalized system. Recognizing the major role of the territories in the transition thus calls for new capacities for managing and benefiting from the flows going through the territories.