Clearing your house of English ivy—even after the plant has died—can be tough, if not impossible. Patches of brick and plaster have been known to come off buildings before the green-leaved vine surrenders its grip. More than 130 years ago, Charles Darwin discovered that ivy’s sticking power is thanks to a thin yellow glue secreted from its roots. But since then, little has been known about how the adhesive works. Now, after an 8-year investigation, scientists report the mechanism today in the Proceedings of the National Academy of Sciences. The glue’s secret ingredients are tiny balls of sugar-coated proteins. These nanoparticles are highly uniform, allowing them to spread out and work their way into nooks and crannies of surfaces. Once the adhesive’s water evaporates, the nanoballs concentrate, and with the help of other materials, including calcium and pectin, the glue hardens. The research team thinks mimicking the approach could yield some new high-strength adhesives—and might even work in tissue engineering to stick cells to scaffolds when building artificial organs. The nanoparticles also have potential as safer targeted drug delivery systems. Unlike many of the current nanomaterials used to ferry chemotherapies into cells, the ivy nanoparticles don’t contain metal, which can be toxic.