Recent advances in developmental science can teach us a great deal about the value of specific kinds of human interactions in the earliest years of life for the developing brain architecture. Animal experiments indicate that enriched environments with opportunity for frequent interaction and new experiences can help the animals' brains develop more healthy connections. Similarly, when adults engage in give-and-take interaction with babies, it provides a solid foundation for social, emotional, and self-regulatory development. The value of such interaction with a wide range of loving, attentive adults in the family and beyond pays indisputable dividends for the child later in life. Using this science to inform public policy could shape what we emphasize to ensure quality child care and early childhood education, how we structure parental leave policies, and how we break the cycle of poverty.