What if the goal of child health services was not "merely" treating, or even preventing, childhood diseases and disorders, but was expanded to that of promoting children's optimal healthy development? Pediatrics has evolved from an exclusive focus on the treatment of illness to the opportunity to promote children's healthy development. This evolution has profound implications for the content of child health services and programs, for system transformation, and for public policy. Enhanced understanding of the impact of social determinants on children's health and developmental outcomes underscores the importance of an evolving framework for system transformation with key policy implications.