A vital and productive society with a prosperous and sustainable future is built on a foundation of healthy child development. Health in the earliest years--beginning with the future mother's well-being before she becomes pregnant--lays the groundwork for a lifetime of vitality. When developing biological systems are strengthened by positive early experiences, children are more likely to thrive and grow up to be healthy adults. Sound health also provides a foundation for the construction of sturdy brain architecture and the achievement of a broad range of skills and learning capacities. The knowledge base summarized in this document presents a compelling rationale for fundamentally rethinking the health dimension of early childhood policy. Simply calling for a more comprehensive approach to the challenges facing disadvantaged young children and their parents, however, offers nothing new. Equally important, enhanced coordination across systems that are guided by disparate values and disconnected bodies of knowledge is unlikely to produce sufficiently greater impact. What is needed instead is creative new thinking about how to apply a unified science base about the early childhood origins of health, learning, and behavior across multiple sectors. The framework presented in this document is offered in the spirit of attempting to catalyze such innovative policymaking and creative interventions. [For the related report, "The Foundations of Lifelong Health Are Built in Early Childhood: Summary of Essential Findings", see ED515138.]