This paper examines the development of science content knowledge of elementary teachers (N=25) as a result of participating in a summer science Institute funded by the Massachusetts Department of Education and the National Science Foundation. The institute was designed to integrate the physical, life, and earth sciences by addressing the National Science Education Standards (NSES) K-4 and 5-8 content standards related to light. The goals of this research were to discover what teachers with little or no formal science education know about light and vision, explore if and how teachers' understanding of these topics changed during the course of the institute as a result of the pedagogy employed, and probe teachers' understanding of light and vision 2 months after the completion of the institute. Questions raised by this research pertain to whether or not elementary science should be handled by science specialists rather than poorly trained teachers, and whether the focus of elementary science education should be on helping students to become wonderers and explorers of science rather than emphasizing specific content. Contains 14 references. (DDR)