National parks are lauded as "America's best idea" and celebrated for their cultural history and unparalleled scenery. Yet their illustrious scientific history remains largely untold. How many people know that DNA testing owes its origins to a heat-loving bacterium swimming in Yellowstone's springs? Or how sleep science began when a pair of researchers slumbered for a month in Mammoth Cave?Our Natural Lab weaves together stories from physics, chemistry, climate science, ecology, biotechnology, anthropology, astronomy, geology, psychology, and traditional ecological knowledge to examine national parks as among the essential settings for science in the history of human inquiry.We learn how Yosemite and Olympic built climate science's famous Keeling Curve and how plate tectonics owes its "aha" moment to Pinnacles and Mauna Loa. We tour California probing origins, where Lassen's volcanic mud might reveal secrets of life's source, and in a Channel Islands canyon we find some of the continent's oldest human bones. We visit vulnerable glaciers and sequoias, thriving otters and wolves, and forests and rivers where ecology finds its origins in 10,000 years of traditional knowledge. Our Natural Lab poses questions of the future, too: could an acid-loving fungus unlock the key to sustainability? Can a Kilauea rover guide a drone to search for life in lava tubes? Are desert dark skies like at Arches really antidotes to depression?The lesson of Our Natural Lab is clear: if we preserve and protect these special places, future generations will continue to write remarkable stories of science in America's national parks.