Word on what experts are calling a "milestone in medicine": Doctors have successfully repaired a woman's windpipe by transplanting a segment of a new trachea built from her stem cells. The patient, Claudia Castillo, suffered from long-term tuberculosis, and the only other option was a left-lung removal, which carries a high mortality risk. The new trachea was built by taking the windpipe of a donor, killing off its natural cells, and then filling its collagen structure with cells from Castillo's windpipe and stem cells. One surgeon said the transplanted segment was "almost indistinguishable" from the patient's normal trachea. Another said, "Surgeons can now start to see and understand the very real potential for adult stem cells and tissue engineering to radically improve their ability to treat patients with serious diseases."