An inquiry-based approach to watching videos of children engaged in learning, supported by tools that allow for frequent and close viewing, provides an opportunity for prospective teachers to develop their skills of observation and interpretation before entering the classroom. The in-depth study of videos creates a context in which teachers can act as researchers by gathering evidence, developing hypotheses, and coordinating this information as a guide for further inquiry and teaching. This article examines the impact on teacher learning of a Web-based video analysis system called VITAL (Video Interactions for Teaching and Learning) developed by the Columbia Center for New Media Teaching and Learning. (Contains 3 figures.)