Every living thing spreads an invisible signature across its landscape, whether it’s a badger ambling through the grass, an oak growing in the forest, or an eagle soaring overhead. Fur, feathers, skin cells, spores, pollen—all of it is loaded with genetic information that floats away into a data-rich atmospheric soup. Scientists call this information environmental DNA, or eDNA, and it is so potent that in January 2022 researchers announced they’d been able to identify the species in two zoos just by sampling eDNA in the surrounding air.