Writing with contagious enthusiasm, biologist Meg Lowman describes her pioneering tree-climbing expeditions. As she explains, foresters have long ignored the forest canopy, sizing up the trees from eye level only. She ventured higher, exploring the “riotous variety” of life on the rainforest treetops in bold contrast to the “gloomy forest floor” where sunlight is scarce. Gently rigging the tall trees to avoid breaking branches as she climbs, she returns with insights into the increasingly fragile biosystem as wild forests shrink in the face of uncontrolled human consumption.