Swarms of spherical nanobots barely larger than a virus could one day save hundreds of thousands of lives globally each year by staunching deadly bleeds in the brain.

An international team of researchers, led by clinicians from Shanghai Jiao Tong University and the University of Edinburgh, developed the magnetically-controlled devices to deliver precise doses of clotting agents through a body’s blood vessels to prevent blow-outs.

In a demonstration of their potential effectiveness, billions of the drug-carrying microscopic structures were guided through a test animal’s body to safely defuse a model aneurism in its carotid.