The movie Fantastic Voyage, the story of a miniaturized team of doctors traveling through blood vessels to make lifesaving repairs in a patient’s brain, was pure science fiction when it came out in 1966. By the time Hollywood remade the film in 1987 as Innerspace, a comedy, real-world engineers had already begun building prototypes of pill-size robots that could voyage through a patient’s gastrointestinal tract on a doctor’s behalf. Patients began swallowing the first commercially built pill cameras in 2000, and since then doctors have used the capsules to get unprecedented views of places, such as the inner folds of the small intestine, that are otherwise difficult to reach without surgery.