This study explores a third-grade teacher's (Deb) developing knowledge and practice for incorporating representations into her teaching of science over the course of 2 years. Data was gathered from the same science unit (Rock Formation) over 2 years, and consisted of video of seven lessons, one of which was the same lesson taught over both years. Also collected were artifacts from the lessons, pre (planning) and post (reflection) lesson conversations for each of the seven lessons, and interviews conducted with Deb before and after her teaching of the full unit each year. The results showed Deb's learning process of using representations was multi-faceted and incremental. Even with using the same representation forms and/or activities, in the second year, Deb was able to: (1) incorporate representations on multiple aspects of teaching such as reviewing previous knowledge, introducing new topics, and assessing students thinking; (2) use multiple representations in one aspect of teaching; (3) engage students in higher levels of learning. These changes were related to Deb's reasoning of selecting representations, which are described further in the paper. This research contributes to an emerging knowledge base on what teachers know and are able to do with incorporating science representations into their practice. It also contributes to the field of science teacher professional development and the need for considering the multi-faceted nature of teacher learning. Implications for teacher professional development are discussed.