Professor Mao Yilei from Peking Union Medical College Hospital and Professor Michael Millis from the University of Chicago first met in 2006. Over the years, their institutions have maintained close exchanges and cooperation, co-hosting an annual liver surgery conference that gathers medical experts from around the world to explore the latest advances in scientific research and surgical practice. Their friendship has endured for nearly 20 years. Asked to sum up their relationship in a single sentence, Mao quoted a Chinese saying: "True friendship is simple and steady like water."