This study explores what we do and do not know about the roles that ‘informal childcare' play for different families. It shows how these have evolved over the past decade - and discusses how they may continue to evolve - in the light of demographic and policy changes. It documents what is and is not known about the quality of ‘informal childcare' and its effects on child development. And it assesses the economic arguments for state support of informal childcare. The report combines new empirical analysis (of the Childcare and Early Years Survey of Parents, the Millennium Cohort Study, the British Social Attitudes Survey and the Labour Force Survey) with a review of the published quantitative and qualitative evidence.