Alexander Kendrick stands in the Lake of the Clouds after testing his invention. He and the team of cavers executed the deepest known digital communication ever to take place in the United States. Brad Horn for NPR hide caption

itoggle caption Brad Horn for NPR

The bdelloid rotifer Philodina gregaria. Bdelloid rotifers are tiny invertebrates that reproduce asexually. Courtesy of Micrographia hide caption

itoggle caption Courtesy of Micrographia

Water in the atmosphere traps heat, like glass in a greenhouse. When there's less water vapor in the atmosphere, less heat is trapped. Space Frontiers/Getty Images hide caption

itoggle caption Space Frontiers/Getty Images

An artist's rendition of two Sinosauropteryx dinosaurs, showing their short, bristle-like feathers along the midline of the head, neck, back and around the tail, forming irregular stripes. Chuang Zhao and Lida Xing hide caption

itoggle caption Chuang Zhao and Lida Xing

Workers ride past cooling towers at a coal-fired power plant on the outskirts of Beijing. Such power plants are at the center of a debate about the future of energy production in China and the U.S. Frederic J. Brown/AFP/Getty Images hide caption

itoggle caption Frederic J. Brown/AFP/Getty Images

An artist's rendering of a NASA Mars Exploration Rover on the surface of Mars. The robotic explorer Spirit has been stuck in sandy soil on Mars since April 2009. NASA/JPL-Caltech hide caption

itoggle caption NASA/JPL-Caltech

Tools like these ax heads from Vinelz, Switzerland, were used by Neolithic farmers and may have been part of their sex appeal to hunter-gatherer women. Sandstein via Wikimedia hide caption

itoggle caption Sandstein via Wikimedia