The elementary science teacher educators in this article set recognize the challenges that new science teachers face when they enter classrooms. They have developed frameworks and strategies aimed at helping the preservice teachers with whom they work become "well-started beginners" who are ready to address problems of science teaching. To do so, these educators purposefully engage the candidates in focused dialogue regarding challenges or problems of practice that they will likely face in their work. These challenges include (1) engaging in science, (2) organizing instruction, and (3) understanding students. The science teacher educators use a dialogic third space to help the preservice teachers reconsider and develop deeper understandings of these problems of practice. In this introduction, we point out some of the common themes that tie these articles together, including (a) a focus on problems of practice in elementary science teaching, (b) a focus on dialogue with preservice teachers about these problems of practice, (c) a commitment to developing tools and approaches that support principled reasoning about these problems of practice, and (d) a commitment to shared goals and methods for research on elementary science teacher education. We point to ways that these themes are addressed in the three articles.