In a Johns Hopkins laboratory last year, a robot performed the hardest stretch of a gallbladder removal with no human hand on the controls. The system, called SRT-H, worked through 17 distinct steps: identifying the cystic duct and artery, placing clips and cutting tissue in the right order. Across eight ex vivo pig gallbladders it succeeded every time, results its makers published in Science Robotics. The caveat lives inside the phrase ex vivo. The tissue could not bleed, breathe or push back, and a surgeon stood by throughout. Even so, for the delicate core of a real procedure, the machine needed nobody.