An “environment of relationships” is crucial for the development of a child’s brain architecture, which lays the foundation for later outcomes such as academic performance, mental health, and interpersonal skills. However, there is a greater need for policies that consider the importance of adult-child relationships for child well-being. This working paper from the National Scientific Council on the Developing Child explains how these relationships shape child development, and identifies ways to strengthen policies that affect those relationships in the early childhood years.