“Hub trees”—a name for the oldest and tallest trees with the vastest root systems—have better access to sunlight than other trees and this leads them to create excess sugar. That sugar is distributed through their roots, underground, to fungi. These fungi, that need sugar to survive, spread their threads (known as Mycelium) through the root system of trees to absorb excess sugar. In return, the Mycelium enter the root’s innermost point and exchange water and nutrients for the stolen sugar. This connection, as it spreads just below the surface of the earth, becomes a symbiotic web—used for communication, exchange and crisis management. Dubbed mycorrhiza, this system lets trees “talk.” Learn more about their language on NatGeo.