Kristen Bieda is an associate professor of Teacher Education and Mathematics Education at Michigan State University. She also holds an appointment as the Associate Director of Mathematics for the CREATE for STEM Institute. Prior to her appointment at Michigan State, she taught mathematics at the middle school, high school and community college levels. Her research interests include understanding how to incorporate mathematical justification into school mathematics, particularly at the middle school level. She is also interested in the design of clinical experiences that support prospective teachers in learning to teach ambitiously. She is currently the subject area leader for secondary mathematics for Michigan State’s secondary mathematics teacher preparation program. AnnaMarie Conner is a professor of Mathematics Education in the Mary Frances Early College of Education at the University of Georgia. She investigates teachers’ beliefs and identity construction during teacher education and how teachers learn to support collective argumentation in mathematics classes. These two lines of research come together in findings describing how teachers’ beliefs impact their classroom practice with respect to collective argumentation. Dr. Conner’s work investigates the complex connections between teacher education, teacher characteristics, and teacher practice. She is currently collaborating with secondary mathematics teachers in supporting mathematical arguments as well as investigating how elementary teachers navigate infusing argumentation into integrative STEM instruction. Karl W. Kosko is an associate professor of Mathematics Education at Kent State University. His work focuses on how mathematical meaning is conveyed, and has addressed classroom argumentation and discourse, multiplicative reasoning, and use of representations of practice in teacher education. Megan Staples is an associate professor of Mathematics Education in the NeagSchool of Education, University of Connecticut. Her teaching focuses on the preparation of secondary math teachers. Her research focuses on how teachers organize classroom environments that support powerful practices such as collaboration, justification and argumentation. She has served as PI and Co-PI on multiple grants focused on justification and argumentation including the NSF-funded JAGUAR project, and a state-level Math-Science Partnership grant, Bridging Math Practices.