We describe three major challenges that teachers of STEM subjects face in their preparation and practice. Then, we discuss how technology could become a vehicle for providing timely and content-related support. To this end, we suggest a theoretical framework, which builds on the works of Vygotsky, Shulman, and Mishra and Koehler. Specifically, we use the notion of zone of proximal development to accentuate educators' professional growth and ideas from the activity theory to put educators' deliberate actions and learning in the wider context of peer learning. Then, we use this framework to describe two professional learning models, each from a different STEM field. This paper will be of interest to STEM educators and facilitators of professional learning activities, as well as developers of education technology resources.