Elizabeth Holmes (February 3, 1984 - Present)

At age 31, Elizabeth Holmes is the world's youngest self-made female billionaire. Her uncle's death from cancer moved her to develop a way to detect diseases earlier. She dropped out of Stanford University her sophomore year and founded Theranos in 2003 to make cheaper, easier-to-use blood tests. With a virtually painless prick of the finger and a few drops of blood, her labs can quickly run a multitude of tests at a fraction of the price of commercial labs. Holmes raised $400 million from venture capitalists in 2014, valuing the company at $9 billion; her 50% stake is worth $4.5 billion. Some scientists have criticized Theranos for not publishing peer-reviewed studies, but the company got FDA clearance in July 2015 for a herpes test, and a waiver allowing non Theranos or Clinical Laboratory Improvement Amendments (CLIA)-certified locations to use its test.

As of 2014, Holmes had 18 US patents and 66 non-US patents in her name and is listed as a co-inventor on over one hundred patent applications. She is the youngest self-made female billionaire on the 2014 Forbes 400 list, with an estimated net worth of $4.6 billion!