Scientists discovered a 407-million-year-old fossilized fungus living inside one of Earth’s earliest land plants. Using advanced imaging techniques, they confirmed it was an arbuscular mycorrhizal fungus (AM fungus), the same type that still helps modern plants absorb nutrients today. This ancient species, Rugososporomyces lavoisierae, formed tiny tree-like structures inside plant cells — clear evidence that plants and fungi were partnering for survival extremely early in Earth’s history. The finding shows that this nutrient-sharing relationship helped plants thrive on land long before soils or forests existed.