Framed within a relational developmental systems model, the 4-H Study of positive youth development (PYD) explored the bases and implications of thriving across much of the second decade of life. This special issue pertains to information derived from the recently completed eight waves of the 4-H Study of PYD, and presents findings about the relations between individual and contextual variables that are involved in the thriving process. This introduction briefly reviews the historical background and the theoretical frame for the 4-H Study and describes its general methodology. We provide an overview of the articles in this special issue and discuss the ways in which the articles elucidate different facets of the thriving process. In addition, we discuss the implications of this research for future scholarship and for applications aimed at improving the life chances of diverse adolescents.