This 13 SIGICR Classification Workshop provides an opportunity for reflection on the challenges that we face as researchers in an applied field. In considering the papers of the previous 12 American Society for Information Science and Technology (ASIST) Special Interest Group (SIG) in Classification Research (CR) Workshops as well as those of the International Society for Knowledge Organization (ISKO) Conferences from the point of view of systems thinking (Emery, 1969), several themes (among others) emerge. These include 1) the tension that exists between stability and change in systems of knowledge organization, 2) the view of knowledge organization schemes as vehicles for learning and exploration as people engage in information search, and 3) the problem of maintenance of knowledge organization schemes as the world turns. These themes are all related through the challenge that we face in designing structures (e.g., metadata arrays, classifications, displays) that not only support people's tasks and problem solving, but which include self-referential actions to renew, update, or recreate the structures themselves as new technologies, ideas, and inventions arise and old ones fade from consideration.