Nutrition is vitally important both during pregnancy and during a child's early years. Inadequate nutrition during this critical period can harm children's health and developmental outcomes throughout childhood and into adulthood. Thus, write Diane Whitmore Schanzenbach and Betsy Thorn, it's particularly important that young children have adequate nutrition and resources. Yet many young children in the United States lack adequate nutrition. In this article, Schanzenbach and Thorn lay out the extent of the problem and review what the research tells us about inadequate nutrition's detrimental effects on young children's development. They report on the effectiveness of policies and programs that aim to improve nutrition among young children--especially the Supplemental Nutrition Assistance Program (SNAP) and the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC)--as well as supplementation of nutrients (both mandatory and voluntary) by the manufacturers of food products, primarily grains. Finally, they suggest how policy makers and others could help more young children, especially the most vulnerable, get the nutrition they need.