This paper, presented at the 2017 meeting of the National Association for Research in Science Teaching (NARST), summarizes findings from efforts to elicit pedagogical content knowledge (PCK) from elementary teachers. The paper focuses on teachers' knowledge for teaching about the small particle model of matter and is a product of the Knowledge Assets to Support the Science Instruction of Elementary Teachers (ASSET) project. ASSET is exploring a method for collecting and synthesizing pedagogical content knowledge (PCK) from multiple sources, including teachers and research literature.