David Haskell has won acclaim for eloquent writing and deep engagement with the natural world. Now, he brings his powers of observation to the biological networks that surround all species, including humans. Haskell repeatedly visits a dozen trees, exploring connections with people, microbes, fungi, and other plants and animals. He takes us to trees in cities (from Manhattan to Jerusalem), forests (Amazonian, North American, and boreal) and areas on the front lines of environmental change (eroding coastlines, burned mountainsides, and war zones.) In each place he shows how human history, ecology, and well-being are intimately intertwined with the lives of trees. Scientific, lyrical, and contemplative, Haskell reveals the biological connections that underpin all life. In a world beset by barriers, he reminds us that life's substance and beauty emerge from relationship and interdependence.