Labeling system user interface. The WebMILL website (A) provides the ability to select regions (1), navigate training versus testing modes (2), read tutorial and reference material (3), optimize computer setup (4), participate in multiple projects (5), and track progress (6). A light weight applet (B) provides for interaction with imaging data (7) with multiple drawing tools (including brush sizes, advanced zoom, undo/redo, and coloring options) (8), and provide a localizer/hint image (9), an area for detailed instructions (10), and ability to navigate tasks (11).