Mathematics teachers as self-regulated learners and mentors in online problem-solving forums. Nelly Keller is a PhD graduate, jointly supervised by Dr. Zehavit Kohen and by Prof. Boris Koichu from the Weizmann Institute. The research explored the professional development of mathematics teachers in their dual roles as learners and as teachers, in an innovative learning environment including a combination of online interactions and traditional classroom learning. Nelly has vast experience in teaching mathematics in high school and at the Technion Preparatory School, and is involved in the national “Promotion 5” program designed to promote advanced mathematics education at the level of five units. Additionally, she lectures in teacher training courses and practices at the Technion’s Faculty of Mathematics. Nellie received the Avital Award for Excellence and Creativity in Mathematics Teaching, a Trump Foundation Award for Quality Teaching, and is an outstanding practitioner in the Faculty of Mathematics at Technion. Several articles and study materials have been published by her in the field of mathematics education. She holds a bachelor’s and master’s degree in applied mathematics.