Many learning environments involve rituals for rehearsal and reflection. Musicians, for instance, spend countless hours practicing scales and adjusting their bodies to increase their skills. But they do more than simply practice: They also play for instructors and others who can provide valuable critiques of their performances. Architectural design studios encourage students to create designs and share them with experts and peers in organized "crit" sessions that point out good and bad aspects of their work. Athletic coaches often watch videos of games with their players to reflect on issues for improvement. In all cases, there is a cycle of skill rehearsal followed by periods of critical reflection to understand successes and failures, ultimately to improve future performance. The research considers the importance of making actions into artifacts for reflective thinking. In particular, this paper describes ongoing efforts to develop computer-based visualizations for diabetes health management. Approximately 17 million American suffer from diabetes (NIDDK, 1998), and those numbers continue to increase. The disease cannot be cured, but it can be managed through insulin and oral medications and changes in diet and exercise habits. The paper focuses on the latter part of diabetes self-management, the regulation of daily routines to prevent abnormal blood sugar levels that could lead to future health complications. The authors' hypothesis was that diabetics could begin to engage in reflective thinking around their health practices when provided with visualizations that point out potential correlations between blood sugar levels (captured by glucose meters) and behaviors (captured in photographs). The paper reports results from a recent study of the use of visualizations of behavioral and physiological data to enhance the aspects of reflection stated in findings.