The importance of investment in children’s pre-school years for their later life outcomes is increasingly recognised by policymakers. This column surveys the evidence on early childhood development policies in both developed and developing countries. Research suggests that effective education programmes can be implemented at scale even in low-income settings, but the quality of the service and adapting it to the local context are crucial. Sustaining the gains from intervention in the ‘early years’ is also likely to require continuing investment at later stages of childhood.