The MadSci Network, offered through Washington University Medical School in St. Louis, offers a fascinating tour of the human body using digitized images generated by the National Library of Medicine's Visible Human Project. The tour begins with an introduction to the different planes of section, and offers tips on getting a 3D sense of structures from 2D cross sections. The tour continues with the digitized images, thoughtfully accompanied by descriptive details (click on a structure for these "interactive annotations."