You may remember the 1966 film Fantastic Voyage, in which a futuristic submarine and crew were shrunken small enough to travel through a man's bloodstream and pulverize a blood clot from the inside. While we still cannot shrink people, tiny robots are in development to do medical work from the inside of bodies here in the real world.
These microscopic robots are made of hydrogel, in the shape of fish, crabs, or butterflies to see which shapes can best deliver chemotherapy drugs to cancerous sites. They are coated in magnetic nanoparticles, and after injection are steered to the cancer by magnets outside the body. They are programmed to release the drugs when they encounter a more acidic environment near a tumor. So while these are not exactly autonomous robots, they could be a miracle for targeting medication.