This book documents the first five years of life of the children of the influential Millennium Cohort Study, which is tracking almost 19,000 babies born in 2000 and 2001 in England, Scotland, Wales and Northern Ireland. This book is the second in a series of books which will report on the findings from the data and follows on from Children of the 21st century: From birth to nine months (The Policy Press, 2005). It takes an extended look at the children's lives and development as they grow and begin formal education, and the implications for family policy, and service planning in health and social services. The chapters in this book are written by experts across a wide range of social science and health fields and form a unique look at the early lives of children that cuts across disciplinary boundaries. It is essential reading for academics, students and researchers in these fields. It will also be of relevance to policy makers and practitioners with an interest in children's early years, family life, child development, child poverty, childcare and education and health care.