Inspired by a type of mucus secreted by slugs, researchers have developed a sticky but flexible substance that effectively seals wounds after surgery. Adhesion to wet and dynamic surfaces, including biological tissues, is important in many fields but has proven to be extremely challenging to develop. Existing adhesives can be toxic, adhere weakly to tissues, or cannot be used in wet environments. In the search for an adequate substance that can overcome these challenges, Jianyu Li and colleagues were intrigued by a defensive mucus secreted by slugs (Arion subfuscus). They developed a family of tough adhesives (TAs) that mimic the properties of the mucus, which consists of a tough, yet flexible matrix and an adhesive surface containing positively charged polymers. The polymers adhere to substances through a range of physical mechanisms, including via covalent bonds, making them particularly sticky. The newly developed TAs adhere strongly to pig skin, cartilage, heart, artery, and liver. Furthermore, the substances were not found to be toxic to human cells. The researchers then used one of the bio-inspired products to seal a defect in a pig heart that was slick with blood. They report that the sealant conformed well to the heart and did not leak as the heart was inflated, exerting a 100% strain on the sealant. In experiments in rats simulating emergency surgery and sudden blood loss, the authors found that their TA's performance was comparable to using a hemostat, a tool used in many surgical procedures to stem bleeding.