This paper tests the utility of a new sociocognitive frame for analysing the development of teachers' knowledge--the knowledge integration perspective (Linn, Eylon, & Davis, in press; Linn & Hsi, 2000). In doing so, the paper describes one prospective elementary teacher's developing knowledge and highlights its complexity. The prospective teacher demonstrates relatively well-integrated science subject matter knowledge, but she makes some problematic links to lessons and develops some instructional representations that show where she needs to distinguish between different scientific ideas. She also, however, links science concepts to appropriate real-world experiences, indicating that she has nascent useful pedagogical content knowledge. The paper discusses what teacher educators can learn about their learners from this analysis, argues for the utility of the knowledge integration perspective for conducting similar analyses, provides ideas to help science teacher educators apply the perspective easily as they teach their students, and points to areas ripe for future research.