The blood-testing startup is billed as a classic industry disruptor - offering a cheaper, more efficient alternative to traditional medical tests. Theranos, founded in 2003, claimed it could "quickly process the full range of laboratory tests from a few drops of blood." But last month, the Wall Street Journal published a front-page investigation questioning Theranos' blood tests - the core of its business. If you're just catching up, here's what you should know: On October 15, the Journal reports that Theranos is using its proprietary technique on only a small number of the 240 tests it performs. The upshot is a seeming blockbuster: The vast majority of Theranos' tests are done with traditional vials of blood drawn from the arm, not the "few drops" taken by a finger prick. Holmes also publicly addressed vocal critics like Google Ventures manager partner Bill Maris: "We have never met them and, in fact, they reached out to meet us and we said no. ... If he wants to just talk badly about us, he can just talk badly about us."