This report contains scenes of surgery.
A paralysed man has been able to walk again after a pioneering therapy that involved transplanting cells from his nasal cavity into his spinal cord.
Darek Fidyka, who was paralyzed from the chest down in a knife attack in 2010, can now walk using a frame.
The treatment, a world first, was carried out by surgeons in Poland in collaboration with scientists in London.
Fergus Walsh reports.
The Panorama special – To Walk Again is on BBC One tonight at 10:35.