Mehmet Oz, President Donald Trump’s nominee to lead the agency that oversees millions of Americans’ health insurance, faced questioning from senators Friday.

Dr. Mehmet Oz goes in front of Senate committee for confirmation as leader of U.S. Centers for Medicare and Medicaid Services. Here’s a look at his background.

Oz’s testimony was the first step in securing the votes to become head of the Centers for Medicare and Medicaid Services (CMS).