Interventions to enhance development of children ages 0-6 have profound benefits for children, families, and societies. The benefits are well documented, recognized internationally, and supportive of policies and programs targeting early child development (ECD). Intervening in the early years is a critical first step toward alleviating poverty, reducing inequality, and ensuring a productive workforce for the global economy. The challenges presented by the almost 250 million at-risk children in low- and middle-income countries and the main obstacles to investing in ECD demand a paradigm shift in social policy and an action agenda integrated with the world's sustainable development goals for 2030. There are four main tasks and three essential building blocks for ECD action.