The authors’ wish is for more long-term longitudinal studies specifically designed to demonstrate the importance of adolescence in the life course. Specifically, the authors wish for their science to document as rigorously as possible the individual and contextual characteristics and experiences that matter the most during adolescence for long-term adult health and well-being. Recent research has shown the early childhood effects on adult outcomes, including effects from intervention programs, bringing needed scientific evidence to inform social policy about the importance of optimizing early development. In most of these efforts, there is little emphasis on adolescence, and thus there is little understanding about the effects of adolescence over and above the effects of childhood on adult outcomes. The authors’ view is that adolescence matters a great deal for long-term health and well-being and they summarize what it will take to make their wish come true.