Many life outcomes – ranging from employment to health to crime – have their roots in the early years. Children are most sensitive to their environment in early childhood, when the foundations for healthy cognitive, social, emotional, and physical functioning are laid. Our research in this area focuses on understanding how the investments made by parents, childcare settings, schools, and government in the early years influence child development, and on analysing the role that early years policy can play in improving child development and later-life outcomes. Both in the UK and in lower- and middle-income countries, we investigate how skills evolve over the lifecycle and the drivers of inequalities in outcomes in childhood and later life. We use a variety of methods to assess programmes to promote child development, both evaluating existing services and piloting new interventions.