Dr. Karen Fuson was a member of the National Research Council’s Committees that wrote Adding It Up, Mathematics Learning in Early Childhood: Paths Toward Excellence and Equity, and How Students Learn: Mathematics in the Classroom. Professor Fuson worked on the Common Core State Standards-Math and on the learning progressions for these standards and has advised PARCC and Smarter Balance on their math test design and items. She has published over eighty research articles on mathematics teaching and learning. Dr. Steven T. Smith was a post-doctoral researcher on the Children's Math Worlds Research Project. He has worked with many teachers and hundreds of students supporting learning in the early grades.