We've seen robots designed to move inside bodies before. Carefully shaped magnetic objects, these miniature robots are moved by external magnetic forces, like those found in MRI machines. Last month, researchers from Boston Children's Hospital and the University of Houston demonstrated a system of small magnetic "millirobots" designed not only to swim through a person's bloodstream and spinal fluid, but assemble into an electromagnetic gun once inside.

The goal is have doctors guide these robots through a patient's body and direct them to trouble spots — fluid buildup, blocked passageways, injuries — and and use them to inject drugs or relief directly into the affected areas. As IEEE Spectrum reports. The robots aren't yet at a bloodstream scale, so here's video of them simulated in a larger body of water: