The purpose of this chapter is to present the theoretical and empirical foundations of a relatively recently emerged conception of youth. Termed the “positive youth development” (PYD) perspective, the orientation to young people has arisen because of interest among developmental scientists in using developmental systems, or dynamic, models of human behavior and development for understanding the plasticity of human development and, as well, the importance of relations between individuals and their realworld ecological settings as the bases of variation in the course of human development