3D biomedical data obtained through tomography provide exceptional views of the interior structure of biological material. While visualization is one of the primary purposes for obtaining these data, other more sophisticated uses are possible. These include simulation of physical processes, interactive surgical investigation, modeling of tissue interrelationships, and analysis of dynamics. Visualization is merely the first contribution of computers to the display and analysis of these image data. Techniques are being developed to facilitate such advanced uses of 3D and 4D tomographic data.