In recent years, mounting evidence on the importance of early childhood development has led to growing attention to children’s experiences from birth to 8 years of age. In addition to spurring the development of new models to directly support young children and their caregivers, there has also been an increased emphasis on national policies and practices integral to protecting young children’s rights. Yet despite increased attention, millions of young children are still not experiencing the conditions necessary to support their development. Concerted and coordinated action is required, on behalf of young children, to build the infrastructure necessary to ensure that all young children experience the conditions needed to reach their developmental potential. An essential component of this infrastructure is the ability to measure results for children.