Following a brief introduction by Frederick Erickson that includes a moment of silence for the late Brigitte "Gitti" Jordan, the video below (beginning at 15:03) illustrates researchers conducting group "interaction analysis" of a 2-minute video of classroom interaction showing the teaching of a key idea in the physics of matter—that matter occupies space—in a kindergarten-first grade classroom. This video is the same video used by participants in their individual analysis sessions. Commentary about the history and themes of this session is also available here.