University Health Network (UHN) is a medical centre that comprises four hospitals: Toronto Western Hospital, Toronto General Hospital, Princess Margaret Cancer Centre and the Toronto Rehabilitation Institute. These are a network of teaching hospitals affiliated with the University of Toronto Faculty of Medicine. It is a recognized leader in patient care, research and education. UHN has a proud history of achieving many "world firsts" including discovering stem cells, pioneering deep brain simulation to treat patients with depression, performing the world's first single and double-lung transplant and pioneering the Cobalt machine, the technology that allowed modern radiation therapy to develop. UHN is committed to continually breaking new ground in research and treatment so it can enhance patients' experience and outcomes.