Video is increasingly used in professional development programs for teachers. Several studies have shown that the ability to notice and analyze pertinent classroom elements is the mark of an expert teacher, but little research has focused on how to use video to bring about real transformations in teachers' classroom activity. A research program was therefore developed to address this issue, drawing on Dewey's notion of collaborative inquiry and key concepts from work analysis. The research revealed three processes of professional development that video-artifacts can bring to the fore and enrich: mimetic engagement, the comparison and cross-fertilization between activities, and the deconstruction-reconstruction of activity. On the basis of these processes, the researchers designed a program called the Collaborative Video Learning Laboratory, which has yielded promising preliminary results for professional development. The advantages and challenges of this program are discussed and the new perspectives for professional development programs for teachers are presented.