Trees are essential. They provide water, shelter, and food for millions of plant and animal species, including humans. They deliver proven health benefits, and they capture and store carbon, which combats climate change. Yet trees are in trouble. Forests are struggling to adapt to climate change, and deforestation is a major threat. Recently, researchers and citizen scientists made the surprising revelation that trees communicate with each other through an underground system of soil fungi and other methods. Complex social networks help trees survive and thrive by transferring resources to each other, sending defense signals, communicating with their kin, and more. Meet the tree scientists and learn more of their fascinating discoveries.