Mark Driscoll is a nationally recognized leader in mathematics education who designs instructional resources and professional development materials that build mathematics teachers' capacity to enhance students' understanding and improve their learning outcomes. He is the author of Mathematical Thinking and Communication (2016), Fostering Geometric Thinking (2007), Fostering Algebraic Thinking (1999), as well as The Fostering Geometric Thinking Toolkit (2008) - all published by Heinemann. Mark is the Managing Project Director of Leadership for Learning Innovation at Educational Development Center (EDC) in Waltham, MA. He received his Ph.D. in mathematics (differential geometry) from Washington University in St. Louis and taught mathematics at Logos School, an alternative high school in inner-city St. Louis. He has been a member of the writing team for NCTM's Assessment Standards for School Mathematics and served as Editor of Mathematics Education Leadership, the journal of the National Council of Supervisors of Mathematics, from 2003 - 2007. Mark has been named the recipient of the Ross Taylor/Glenn Gilbert National Leadership Award from the National Council of Supervisors of Mathematics (NCSM). The award recognizes Mark's contributions to mathematics education over four decades as well as his work at EDC. Rachel Wing DiMatteo is a coauthor of Fostering Geometric Thinking (2007) and its professional development companion, The Fostering Geometric Thinking Toolkit (2008), both published by Heinemann.Shestudied the development of mathematical knowledge while pursuing her Ph.D. in Psychology (cognitive development). Since then Rachel has been involved in the creation of professional development materials that help teachers understand the development of mathematical knowledge in their students. Johannah Nikula is a coauthor of a number of Heinemann professional development books and staff development materials. Her most recent are Lesson Study in Practice: A Mathematics Staff Development Course (2010) and the companion, A Mathematics Leaders Guide to Lesson Study in Practice (2010). She also coauthored Fostering Geometric Thinking (2007) and its professional development companion, the Fostering Geometric Thinking Toolkit (2008), both published by Heinemann. Her work has focused on professional development for middle and high school mathematics teachers that is grounded in the work of teaching through analysis of artifacts that reveal students' mathematical thinking and through the Japanese lesson-study process. Michael Egan is a coauthor of Fostering Geometric Thinking (2007) and its professional development companion The Fostering Geometric Thinking Toolkit (2008), both published by Heinemann.Hehas taught middle and high school mathematics since 1995. While he continues to teach adolescents on a part-time basis, his current work focuses on mathematics education research and teacher education.