Instead of mixing cocktails at Stanford, Holmes mixed three research projects together to create a device that would help save lives. With the Theranos 1.0, which measures medicine in patients' bloodstream, Holmes hopes to prevent the 100,000 deaths that occur each year from adverse drug reactions. The device is currently being sold to pharmaceutical companies for clinical trials.

Age: 22
Location: Menlo Park, Calif.
Revenue: undisclosed
Employees: 65