This report combines neuroscience, child development research, and program evaluation data to better inform policymakers' decisions about investing in and supporting existing early childhood programs. Core child development concepts highlight the importance of early experiences on the development of brain architecture and, in turn, future learning, health, and behavior. Drawing on analysis of four decades of evaluation research conducted on existing programs for children ages birth to five, the framework also addresses questions about when to invest in the lives of young children and how to do so. Five contexts in which policies can affect how children develop are discussed: (1) The nuclear family; (2) Out-of-home settings; (3) Multi-generational programs; (4) Family economics and maternal employment; and (5) Environmental contamination. Key findings related to these contexts are identified, and specific factors that influence the effectiveness of programs in these areas are discussed. Selected background readings are included. (Contains 188 notes, 7 figures and 1 table.) [Additional sponsorship was provided by the Buffett Early Childhood Fund, the Pierre and Pamela Omidyar fund, and the Johnson & Johnson Pediatric Institute.]