This isn't the first proposed use of tiny surgical robots that could work within the body, but these bots from Johns Hopkins University seem very promising, according to an article in IEEE Spectrum. Instead of taking dozens of samples from the colon with forceps, doctors can deploy hundreds of micro-bots inside the patient's body using a tube inserted in the colon. Depending on what the bots are made of, they can take a tissue sample when exposed to a particular temperature, acidity, or enzyme inside the body. Their arms close around the tissue, removing a bit of it for a biopsy. Later, healthcare professionals can recover the bots by inserting a magnet in the colon or by sifting through a patient's stool. During tests in animals, researchers found that even if only a third of the bots come out with samples, that's plenty for doctors to determine if colon cancer is present.