Using an instrument they've named the HOLODEC, for Holographic Detector for Clouds, scientists can now see in fine detail the way air and water droplets mix at a cloud's wispiest edge. iStockphoto hide caption

itoggle caption iStockphoto

Gulping down coffee to stay awake at night delays the body's natural surge of the sleep hormone melatonin. Hayato D./Flickr hide caption

itoggle caption Hayato D./Flickr

The Antarctic ice sheet stores more than half of Earth's fresh water. Scientists wondered how much of it would melt if people burned all the fossil fuels on the planet. UPI /Landov hide caption

itoggle caption UPI /Landov

National Geographic paleoartist John Gurche used fossils from a South African cave to reconstruct the face of Homo naledi, the newest addition to the genus Homo. Photo by Mark Thiessen/National Geographic hide caption

itoggle caption Photo by Mark Thiessen/National Geographic

A child suffering from dengue fever lies in a bed in the isolation ward of a Rawalpindi, Pakistan, hospital in November 2013. There is no treatment for dengue, whose symptoms include fever, severe joint pain, headaches and bleeding. Muhammed Muheisen/AP hide caption

itoggle caption Muhammed Muheisen/AP

An impala strikes a pose under a forest canopy in Zimbabwe. Morkel Erasmus/Getty Images/Gallo Images hide caption

itoggle caption Morkel Erasmus/Getty Images/Gallo Images

Delegates took their seats during the plenary session at the Bonn climate change conference on March 10, 2014. Negotiations resume this week; by the end of the year, the U.N. hopes to have forged a new global agreement. UNclimatechange/Flickr hide caption

itoggle caption UNclimatechange/Flickr

Male and female tungara frogs. Among these frogs, the guy with the best call usually wins the gal — except when you throw a third-choice loser into the mix. Alexander T. Baugh/Encyclopedia of Life hide caption

itoggle caption Alexander T. Baugh/Encyclopedia of Life

A brown bear in its natural habitat. Wildlife ecologists in Minnesota found that black bears in their study experienced an increase in heart rate when buzzed by drones. iStockphoto hide caption

itoggle caption iStockphoto

A juvenile California two-spot octopus (Octopus bimaculoides). Michael LaBarbera/Nature hide caption

itoggle caption Michael LaBarbera/Nature

Can you guess which eyes belong to what animal? Top row, from left: cuttlefish, lion, goat. Bottom row, from left: domestic cat, horse, gecko. Top row: iStockphoto; bottom row: Flickr hide caption

itoggle caption Top row: iStockphoto; bottom row: Flickr

Ready, set, fly! The ball bearings glued to this bumblebee's legs simulate the weight and placement of pollen loads. The tag on the insect's back is a lightweight sensor, designed to track its movements in flight. Courtesy of Andrew Mountcastle hide caption

itoggle caption Courtesy of Andrew Mountcastle