Elizabeth Holmes founded her revolutionary blood diagnostics company, Theranos, when she was 19. It's now worth more than $9 billion, and poised to change health care. In the fall of 2003, Elizabeth Holmes, a 19-year-old sophomore at Stanford, plopped herself down in the office of her chemical engineering professor, Channing Robertson, and said, Let's start a company." As a freshman, Holmes had taken Robertson's seminar on advanced drug-delivery devices-things like patches, pills, and even a contact-lens-like film that secreted glaucoma medication-but now she had invented one the likes of which Robertson had never conceived. It was a wearable patch that, in addition to administering a drug, would monitor variables in the patient's blood to see if the therapy was having the desired effect, and adjust the dosage accordingly. With Robertson's blessing, Holmes started her company and, a semester later, dropped out to pursue it full-time. Now she's 30, and her private, Palo Alto-based corporation, called Theranos-the name is an amalgam of the words "therapy" and "diagnosis"-has 500 employees. Theranos today is a potentially highly disruptive upstart in America's $73 billion diagnostic-lab industry. It currently offers more than 200-and is ramping up to offer more than 1,000-of the most commonly ordered blood diagnostic tests, all without the need for a syringe. Theranos's tests can be performed on just a few drops of blood, or about 1/100th to 1/1,000th of the amount that would ordinarily be required-an extraordinary potential boon to frequently tested hospital patients or cancer victims, the elderly, infants, [and] children.