This book brings together a collection of research-based papers on current issues in early childhood mathematics education that were presented in the Topic Study Group 1 (TSG 1) at the 13th International Congress on Mathematical Education (ICME-13), held at the University of Hamburg in 2016. It will help readers understand a range of key issues that early childhood mathematics educators encounter today.  Research on early childhood mathematics education has grown in recent years, due in part to the well-documented, positive relation between children’s early mathematical knowledge and their later mathematics learning, and to the considerable emphasis many countries are now placing on preschool education.  The book addresses a number of central questions, including: What is mathematical structural development and how can we promote it in early childhood? How can multimodality and embodiment contribute to early mathematics learning and to acquiring a better understanding of young children’s mathematical development? How can children’s informal mathematics-related experiences affect instruction and children’s learning in different mathematics content areas? What is the role of tools, including technology and picture books, in supporting early mathematics learning? What are the challenges in early childhood mathematics education for teachers’ education and professional development?