The longest bone in the human body, the femur connects to the pelvis at the hip joint. This high-resolution computed tomography (CT) scan of the bone reveals its inner microstructure. The colors denote the mineral volume fraction, which provides a spatial measure of strength and can be used to identify individuals at risk of osteoporotic fracture. For an account of CT’s evolution and advances, turn to the article by John Boone and Cynthia McCollough on page 34 . (Image courtesy of Lance Frazer/Southwest Research Institute.)