Researchers at the University of Maryland School of Medicine say they have performed a pig-to-human heart transplant surgery. The patient is a man with terminal heart disease, and is reportedly doing well three days after being implanted with a genetically modified pig heart. The university obtained an emergency authorization from the U.S. FDA on New Year's Eve for this experimental surgery. It was made possible by new gene-editing tools. It's the first of its kind to demonstrate the feasibility of such surgeries.