The future of civil society in the world rests on the promotion of positive development and a commitment to positive and socially just community contributions by the young (Lerner, 2004). Adolescents represent, at any point in history, the generational cohort that must be prepared to assume the quality of leadership of self, family, community, and society that will maintain and improve human life. As illustrated powerfully by the work described in this article, developmental scientists have a vital role to play in enhancing, through the generation of integrated basic and applied knowledge, the probability that adolescents will become fully engaged citizens who are capable of, and committed to, making these contributions. The work of the Miami Youth Development Project (YDP) exemplifies the idea that contemporary developmental science--predicated on a relational metatheory and developmental systems theories that frame research into dynamic relations between diverse individuals and contexts--constitutes an approach that may integrate the scholarship pertinent to these diverse levels of organization and by so doing may facilitate understanding and the promotion of positive human development. This approach to developmental science underscores the diverse ways in which adolescents, in dynamic exchanges with their natural and designed ecologies, can move along pathways marked by opportunities for health and positive development. As Bronfenbrenner (2005) eloquently puts it, it is these relations that make human beings human.