Macchiarini performed the nine-hour operation on April 9 at the Children's Hospital of Illinois after carefully creating the windpipe using stem cells from Hannah's bone marrow that were saturated over a matrix of plastic fibers shaped into a tube.

CNN: Toddler gets new windpipe from her own stem cells

If we were doing it again now, the material would be taken out in its soil matrix, put in a plastic bag and kept cool.

BBC: NEWS | Science/Nature | Team widens search for 'Hobbits'