SMK and PCK are crucial for effective science teaching, yet the amount of subject matter covered in elementary teacher education programs is limited. This exploratory study of ten elementary school teachers focuses on how teachers learned science content from their teaching practice (including preparing to teach, classroom instruction, and reflecting on teaching). Qualitative analysis of teacher interviews indicates triggering events that influenced teachers' learning new science content, sources teachers sought out for learning, and types of knowledge learned. This process is explained in a model of teacher learning in and from practice derived from the data. Challenges and obstacles to learning are also discussed as well as implications for preservice teacher education, teacher induction and professional development, and curriculum development.