**FILE** Hannah Warren, 2, poses with her parents Lee Young-mi and Darryl Warren at Seoul National University Hospital in Seoul on July 13, 2012. Hannah, who was born without a windpipe, received a new windpipe made from her own stem cells in a landmark operation on April 9, 2013, at Children's Hospital of Illinois in Peoria, Ill. She is the youngest patient ever to get the experimental treatment. (Associated Press/The Korea Herald)

Photo by: Kim Myung-sub

**FILE** Hannah Warren, 2, poses with her parents Lee Young-mi and Darryl Warren at Seoul National University Hospital in Seoul on July 13, 2012. Hannah, who was born without a windpipe, received a new windpipe made from her own stem cells in a landmark operation on April 9, 2013, at Children's Hospital of Illinois in Peoria, Ill. She is the youngest patient ever to get the experimental treatment. (Associated Press/The Korea Herald)