This mixed-methods study examined four STEM communities (BioQUEST, Project Kaleidoscope, the POGIL Project, and SENCER) in order to better understand the roles of these communities in advancing the goals of scaling STEM education reform. The project explored three key questions: (1) How do members and leaders of communities of practice (CoPs1) perceive CoP design (membership, structure, communication, activities, and organization to support new knowledge development and action) shape the ability to achieve goals (around undergraduate STEM pedagogical change and diffusion); (2) What are the perceived benefits of participation in a STEM reform community of practice or network for the individual participants and for their campuses; and (3) How do communities of practice and networks form, and how are they sustained in ways that help them to achieve their goals? The following are the key findings related to these questions: (1) The study identified a novel approach to improving STEM education, which the authors have called communities of transformation; (2) Communities of transformation address both individual faculty and broader systemic change; (3) Benefits of these communities accrue to both individual faculty and to their institutions; (4) Communities of transformation provide significant benefits for women faculty and for faculty of color; (5) Positive outcomes follow from an engaging philosophy that is lived in programmatic activities and fostered through a supportive and mentoring community; (6) Communities of transformation follow similar trajectories as they evolve from an idea to a community; (7) Communities of transformation face common challenges and must develop particular strategies to navigate them; (8) Communities of transformation rely on a specific set of avenues for expanding impact; (9) Future communities of transformation can draw on the sustainability model identified and developed through this study; and (10) There are further ways that communities of transformation can extend their impact. A bibliography is provided.