A Tarrytown mother is beaming after her son won a Nobel Prize for Medicine Monday.

Katherine Semenza's oldest son, Gregg Semenza, won the prestigious honor for his research on how cells manage oxygen.

When he heard the news, the Johns Hopkins professor knew what he had to do first -- call his mom.

Katherine Semenza says her son called at 5 a.m. and she didn't pick up the phone at first.

But when she did hear the news, the proud mother of five told News 12 that she could not stop crying.

"I feel like I'm flying," Katherine Semenza said. "I know when he got into medical school with a scholarship for six years, I felt like I was a foot off the floor but now this is....I don't think it has sunk in yet."

Greg Semenza's work has the potential to treat diseases where oxygen is in short supply, which includes some forms of cancer.