Patrick Hardison’s face burned off while he was working as a volunteer firefighter in 2001. In August 2015, Dr. Eduardo Rodriguez gave him a new one.

It was the most extensive face transplant ever, involving more than 100 people. Dr. Rodriguez’s team practiced for more than a year. Once the operation began on August 16, he took just three short breaks, mostly just because he had to use the bathroom.

“A total face transplant with the scalp had never been done,” Rodriguez, the chair of NYU’s Hansjörg Wyss Department of Plastic Surgery, told Insider. “The eyelids are functioning currently on Patrick — that is a hugely important medical accomplishment.”

This was not Rodriguez’s first face transplant, but it was his most extreme one. The whole procedure took 26 hours: 12 hours to procure the face from the donor, seven hours to remove the scarred face, and ten hours to complete the transplant.

“It’s not like a recipe that we follow,” Rodriguez said. “No one rests until we’re finished. It’s kind of what we’re mentally prepared to do.”

Read the article “The Surgeon Who Performed the Most Extreme Face Transplant Ever Told Us How He Did It” on businessinsider.com.