Hilda Borko is the Charles E.  Ducommun Professor of Education in the Stanford Graduate School of Education, USA. Dr. Borko’s research explores teachers’ instructional practices, the process of learning to teach, the impact of teacher professional development programs on teachers and students, and the preparation of professional development leaders. Her current projects include partnerships with local school districts to improve teaching and professional development in mathematics and science, and to build capacity within the school districts to prepare and support professional development leaders. Her publications include articles in Journal of Mathematical Behavior, ZDM Mathematics Education, International Journal of Science and Mathematics Education, Journal of Research in Science Teaching, Educational Researcher, American Educational Research Journal and other journals and edited volumes. Dr. Borko served as President of the American Educational Research Association andas a member and chair of various committees for AERA, Association of Mathematics Teacher Educators, and Educational Psychology Division of the American Psychological Association. She is a member of the National Academy of Education, where she served on the NAEd Board of Directors, and as chair of the National Academy of Education/Spencer Postdoctoral Fellowship Selection Committee. She is the 2014 recipient of the Excellence in Scholarship in Mathematics Teacher Education Award, Association of Mathematics Teacher Educators.Despina Potari is a professor at the Mathematics Department of the National and Kapodostrian University of Athens, Greece. She has been visiting professor at different universities in Europe and in the USA and member of International Program Committee of PME and CERME.  Her research interest is mainly on the development of mathematics teaching and on the education of mathematics teachers focusing on the relationship between research and practice in the context of mathematics teacher collaboration. Currently, she is involved in projects that focus on the education of STEM teachers through the design of classroom and professional development tasks. She has publications in international research journals, conference proceedings and book chapters. Her publications include articles in Educational Studies in Mathematics, Journal of Mathematical Behavior, ZDM Mathematics Education, International Journal of Science and Mathematics Education.  She is chief editor of the Journal of Mathematics Teacher Education, member of editorial boards and teams and reviewer for international journals and conferences.