Elizabeth Holmes, the youngest self-made female billionaire worldwide , was just 19 years old when she founded her company Theranos, which makes affordable diagnostic blood tests.

Twelve years later, the company is valued at $9 billion, and the entrepreneur recently spoke this week Clinton Global Initiative (CGI) in New York about how to make health care more accessible through her company's FDA-approved home blood tests.

Holmes also spoke out at CGI about how to get more women involved in science-related fields.

"Raise our little girls with the stereotype that they can be the best in engineering and science and math," she said at the closing session of CGI, which brings together global leaders to commit to tackling some of the world's most pressing problems. "It changes everything."

Her comments on the importance of encouraging girls in STEM subjects were met with applause. She stated that more progress needs to be made: "We need to do that in this country, and we need to that as parents in other countries."

Holmes spoke alongside Jack Ma, chairman of Chinese e-commerce giant AliBaba, at the closing session, which was moderated by Bill Clinton and called "The Future of Equality and Opportunity in the 21st century. The panel focused on how technology can increase economic development around the world.

Holmes, now 31, founded Theranos in 2003 when she was a sophomore studying chemistry at Stanford, and dropped out to focus on the company full time. Channing Robertson, her chemical engineering professor, told Inc. magazine that during her freshman year, Holmes would often "nag" him to let her work in his lab, which was otherwise staffed by PhD students. He went on to become her company's first advisor.

Theranos makes over 150 blood tests that retail for less than $10 and test for a variety of conditions from Herpes to pre-diabetes. The tests cost 50 to 80 percent less than their Medicare equivalents, according to CNBC . Given the FDA approval the company earned over the summer, Theranos plans to stock their blood tests in 8,000 Walgreens stores across the nation.

Clinton lauded Holmes's success at making personal health data widely and cheaply available. He called it a development that "would have been unimaginable for all of human history until now.