Indonesia has begun to emerge into middle-income status, yet persistent poverty and stark inequalities continue to affect young children's development. This book tells the story of Indonesia's efforts to change the trajectory of development for poor children. Many countries have similar aims, but several aspects of what is reported here are especially valuable and perhaps unique: The study offers data on all aspects of health and development in a sample of rural young children, collected with internationally-validated measures, as well as household information, information about parenting practices including feeding patterns, parent questionnaires, and data on the prevalence and distribution of ECED services. The data reported in this book is based on a sample of more than 6,000 Indonesian children living in 310 poor villages, including two age cohorts (aged 1 and 4 years old when data were first collected on their development in 2009). From the start, the project aimed not only to support service provision but also to support the development of national standards, build national and district capacity, and encourage the establishment of a system of ECED quality assurance, efforts that are still in process. Few such analyses have been done with such a large sample and with multiple measures. These design features allow a high level of confidence in the results that are reported. The lessons from this book will help to inform not only this project's further implementation but ECED initiatives in Indonesia and around the world. Thus, the results presented in this book are of significance for researchers, policy-makers, and practitioners within and beyond Indonesia. The experiences and research results discussed here are especially relevant for: Researchers in early childhood development and programme evaluation; Policymakers within and beyond Indonesia; Providers of early childhood services; Professional development providers; Advocates for quality early childhood services.