Exposure to deprivation and distress in childhood can have profound and lasting consequences for children as they grow up, but the effects vary widely across individuals and contexts. How much do we understand about child development in these circumstances? It is often assumed that economic development will improve well-being, how have rapid socio-economic transformations impacted on children? And what kind of evidence do policymakers need in order to implement effective interventions that both harness economic growth and also deliver benefits for poor children?