The science of child development and the core capabilities of adults point to a set of "design principles" that policymakers and practitioners in many different sectors can use to improve outcomes for children and families. That is, to be maximally effective, policies and services should: (1) support responsive relationships for children and adults; (2) strengthen core life skills; and (3) reduce sources of stress in the lives of children and families. These three principles can guide decision-makers as they choose among policy alternatives, design new approaches, and shift existing practice in ways that will best support building healthy brains and bodies. They point to a set of key questions: (1) What are current policies, systems, or practices doing to address each principle?; (2) What could be done to address them better?; and (3) What barriers prevent addressing them more effectively? This science-based framework offers a promising guide for generating new ideas about how to meet the objectives of each policy or practice system more effectively--and, in the end, achieve significant improvements in outcomes for the children and families who are the foundation of our communities and our shared future. The science in this report draws principally from the work of the National Scientific Council on the Developing Child. A list of additional resources is provided. [Additional funding was provided by the Chan Zuckerberg Initiative DAF, an advised fund of the Silicon Valley Community Foundation; Genentech; Hemera Foundation; Palix Foundation; and Tikun Olam Foundation.]