Margaret (Peg) Smith is a Professor Emerita at University of Pittsburgh. Over the past two decades she has been developing research-based materials for use in the professional development of mathematics teachers. She has authored or coauthored over 90 books, edited books or monographs, book chapters, and peer-reviewed articles including the best seller Five Practices for Orchestrating Productive Discussions (co-authored with Mary Kay Stein). She was a member of the writing team for Principles to Actions: Ensuring Mathematical Success for All and she is a co-author of two new books (Taking Action: Implementation Effective Mathematics Teaching Practices Grades 6-8 & 9-12) that provide further explication of the teaching practices first describe in Principles to Actions. She was a member of the Board of Directors of the Association of Mathematics Teacher Educators (2001-2003; 2003 – 2005), of the National Council of Teachers of Mathematics (2006-2009), and of Teachers Development Group (2009 – 2017). Victoria Bill is a former elementary and middle school mathematics teacher. She is currently a Fellow and lead of the mathematics team with the Institute for Learning at the Learning Research and Development Center, University of Pittsburgh. She has been designing and facilitating professional development with administrators, coaches and teachers in urban districts for more than 20 years. She also develops curriculum, intervention materials and performance-based assessments. Bill was the Co-Pi on a collaborative research project between researchers from the LRDC, the IFL, and the Tennessee Department of Education in which an instructional Mathematics Coaching Model was developed. Bill regularly speaks at the National Council of Teachers of Mathematics, National Supervisors of Mathematics, and National Council of Teachers of Mathematics Research Conferences. She is co-author of the NCTM best seller Taking Action: Implementing Effective Mathematics Teaching Practices Grades k-5. Michael D. Steele is a Professor of Mathematics Education and Chair of the Department of Curriculum and Instruction in the School of Education at the University of Wisconsin-Milwaukee. He is currently the President-Elect of the Association of Mathematics Teacher Educators. A former middle and high school mathematics and science teacher, Dr. Steele has worked with preservice secondary mathematics teachers, practicing teachers, administrators, and doctoral students across the country for the past two decades. He has published several books and journal articles focused on supporting mathematics teachers in enacting research-based effective mathematics teaching practices. He is the co-author of NCTM’s Taking Action: Implementing Effective Mathematics Teaching Practices in Grades 6-8 and Mathematics Discourse in Secondary Classrooms, two research-based professional development resources for secondary mathematics teachers. He is also the author of A Quiet Revolution: One District’s Story of Radical Curricular Change in Mathematics, a resource focused on reforming high school mathematics teaching and learning. Miriam Sherin is Associate Provost for Undergraduate Education and the Alice Gabrielle Twight Professor of Learning Sciences at Northwestern University. Her research interests include mathematics teaching and learning, teacher cognition, and the role of video in supporting teacher learning. Sherin investigates the nature and dynamics of teacher noticing, and in particular, the ways in which teachers identify and interpret student thinking during instruction. She is the author of The Five Practices in Practice for both Elementary and Middle School, and The On-Your-Feet Guide to Orchestrating Mathematics Discussions.