The world-famous fossil known as SUE is the largest, best-preserved, and most complete Tyrannosaurus rex ever found. Sue Hendrickson, working for a commercial fossil company, found the bones in 1990. The owner of the company nicknamed SUE after her. The specimen eventually became the center of a now-famous custody battle. The Field Museum purchased the legendary specimen at auction in 1997, and SUE soon came to roost in Chicago. Since then, scientists have learned a lot about T. rex, a dinosaur which shares an ancestor with birds. But many mysteries remain, including whether SUE is really a female.