The head of the U.S. National Institutes of Health (NIH) is stepping down amid lingering questions regarding his agency’s funding of research in China. Dr. Francis Collins has served as NIH director for over 12 years in a tenure that has spanned three administrations. “It has been an incredible privilege to lead this great agency for more than a decade,” Collins said in a statement on Tuesday. “I love this agency and its people so deeply that the decision to step down was a difficult one, done in close counsel with my wife, Diane Baker, and my family.” Collins was appointed by then-President Barack Obama on Aug. 17, 2009. Presidents Donald Trump and Joe Biden asked him to remain in the position. Before that, he directed the National Human Genome Research Institute. After stepping down from NIH, he plans to work at the research institute. NIH includes a number of offices, …