that he began climbing and studying redwood forests. Later After moving to northwestern California, Sillett began studying old-growth redwood forests and the biodiversity found in their canopies. Additionally, Sillett studies how water is transported up the tree in an effort to understand the limits to tree height. One of his chief interests is in determining the maximum attainable heights of the 6 tallest tree species. To reach the canopies, he uses an arrow to set a climbing line, then ascends using a modified arborist-style safety swing involving ropes, leather harnesses, and pulleys. Once in the canopy, Sillett and his research crew move about in a style known as skywalking using motion lanyards on a web of climbing ropes. To reach outlying branches, Sillett deploys a Tyrolean traverse between adjacent trees. In addition to studying redwood canopies, Sillett studies other tall forests in the US, Canada, and Australia. He has climbed and measured the tallest of each of the six tallest trees species. Sillett and his team do not disclose precise locations of the world's tallest trees. Sillett allows only students and research team members to climb with him, to maintain both the security of the trees and the safety of fellow researchers. Major accomplishments Discovery of the redwood Grove of Titans in 1998, accompanied by Michael Taylor. Sillett began climbing redwoods in 1987, becoming the first scientist to enter the old-growth redwood forest canopy. He has climbed and measured the height of the tallest known live-topped tree of each of the five tree species known to grow over 100 m (300 ft) tall. In 2006, Sillett measured and verified the redwood Hyperion as the world's tallest tree at 115.55 m (379.1 ft). Previous record-holder Stratosphere Giant is 112.83 m (370.5 ft). Sillett is the first holder of the Kenneth L. Fisher Chair in Redwood Forest Ecology at Humboldt State University. This is the world's first and only endowed chair supporting the study of one tree species. The endowment is designed to promote field research of redwood canopies. Sillett, wife Marie Antoine, brother Scott, and other climbing and research companions including Michael Taylor and Chris Atkins are featured in Richard Preston's book The Wild Trees. The book details some notable climbs, including his first ascent into the crown of a tall redwood tree. Sillett's research has been published in a number of academic journals including Nature, the American Journal of Botany,