The sustainability of each kind of system is performed by a perspective towards the future: if the system is social, so, the sustainability is strictly linked to the generational dimension. It is yet accepted that the definition of the concept "generation" can not be explained by the traditional categories too, so that this work tries to offer some ideas to set these categories and, then, to give a specific role to young people in respect of the sustainability. The proposed reflections stress on some sociological analysis about the new generations, especially those that are linked to the sustainability of the social system and that look at the social action with a nonpresent point of view. This sociological theories review shows some of the most important sociological reflections on the sustainability. These are elaborated through some analytical tools more and more "sustainable" to study the evolution and to experiment with a multi-disciplinary strategy.
Keywords: Social sustainability, young condition, multi-disciplinary approach