A man with terminal heart disease is responding well three days after being given a genetically modified pig heart in a first-of-its-kind surgery. Al Jazeera reports that the surgery, performed by a team at the University of Maryland Medicine in the United States, is among the first to demonstrate the feasibility of a pig-to-human heart transplant, a field made possible by new gene editing tools. If proven successful, scientists hope pig organs could help alleviate shortages of donor organs but could potentially face backlash from some people on religious or moral grounds.