The whitish, slimy trail that slugs leave behind has inspired a novel type of glue—one that’s extremely flexible and compatible with body fluids. Unlike other types of surgical glues, the new class of sealants, dubbed tough adhesives, is nontoxic and sticks to wet tissues such as heart (pictured) and liver, even when their surfaces are covered with blood. This is because the sealant contains positively charged molecules that form stable bonds with biological tissues, researchers report today in Science. To prove how tough the slime-inspired glue is, the scientists used it to seal a large hole in an explanted pig heart. As the heart was filled up with liquid, the adhesive patch expanded with it and did not leak under up to a 100% strain and tens of thousands of cycles of pumping. When the researchers simulated an emergency surgery and sudden blood loss, the glue effectively stemmed bleeding from a rat liver. Tough adhesives could also be injected to fix cartilage discs, the cushions between vertebrae, or used as band-aids to close wounds on pig skin, the scientists say.