Editorial note: Teacher professional development in STEM education

In line with the substantial interest in STEM (science, technology, engineering, and mathematics) education and the major projects in STEM curriculum development around the world, efforts should be particularly made to increase the supply of STEM teachers through proper and effective teacher professional development. Although there have been a number of studies related to teacher professional development for individual subject training in science, technology, engineering and mathematics, quality research on professional development for teachers to develop their capacity for adopting the integrative and cross-disciplinary approaches advocated in STEM education remains in its infancy. The theme of this special issue is two-fold: (a) to provide researchers and practitioners in STEM education with a scholarly platform for reflecting on what challenges and impediments STEM teachers have encountered, and (b) to exchange new theoretical and practical insights gained from empirical research on designing, enacting and evaluating professional development programmes for building teachers' capacity in STEM education. Copyright © 2021 International Forum of Educational Technology & Society.