Reaching and Investing in Children at the Margins is a report from event co-hosted by ISSA and the Open Society Foundations in partnership with the National Academy of Sciences’ Forum on Investing in Young Children Globally in Prague in 2016. During the event top-class speakers from across the world gathered to share their knowledge and open discussions highlighting the science and economics of investing in children at the margins of society by investing in their health, education, nutrition, and social protection. The summary of a joint workshop by the National Academies of Sciences, Engineering, and Medicine; Open Society Foundations; and the International Step by Step Association (ISSA).