Synovial joints have fundamental roles in body function and quality of life. Relatively little continues to be known about joint development such as; how joints acquire their distinct shape and structure, how each joint tissue forms be it articular cartilage or an intrajoint ligament, or how the articular cartilage acquires its stratified organization. Were such basic information available, it could be used to better understand the pathogenesis of joint disease, to test therapeutic tools to recreate the stratified structure of articular cartilage, or to boost the notoriously poor reparative capacity of joint tissues. It could also be used to reprogram stem cells with specific joint tissue repair capacity. This project started nearly a decade ago and focused on the interzone, a mesenchymal structure composed of elongated and tightly associated cells, and has produced fundamentally new insights into synovial joint development.  For instance, using genetic cell tracing and tracking strategies, we have shown that the interzone cells are far from being transient and actually produce joint tissues and only joint tissues over developmental time. A major mechanism endowing the interzone cells with their initial noncartilaginous character is the Wnt/β-catenin signaling pathway. This research has been supported by the National Institutes of Health and we also have initiated research collaboration with NIH scientists.