One of the eight core scientific practices identified by the Next Generation Science Standards to help learners construct understandings of abstract concepts is the development and use of models. In this study we focus on explanatory mental models which are internal cognitive representations of normally hidden mechanisms that can explain why phenomena in a system occur. Our group has studied the model-based strategies used by successful teachers in a wide variety and grade level of conceptually challenging K-12 science topics and we have converged on a set of twelve key cognitive discussion-based teaching strategies that are believed to support students’ conceptual understanding of complex science topics. As a result, the most recent phase of our research has been the development and implementation of an eight-week model-based teaching unit for pre-service science educators that introduces these strategies. The unit also includes videotaped practice mini-lessons that are shared with the pre-service teachers and their classmates for analysis and evaluation. Evidence from pre, post, and delayed post surveys and interviews is presented that indicates how the unit positively impacts the way the pre-service teachers view their developing practice.