Ghanaian fans take a selfie prior to a Group G football match between Germany and Ghana at the Castelao Stadium in Fortaleza during the 2014 FIFA World Cup on June 21, 2014. (Photo by Patrik Stollarz/AFP Photo)

Talk-show host Oprah Winfrey interviewing cyclist Lance Armstrong during taping for the show "Oprah and Lance Armstrong: The Worldwide Exclusive" in Austin, Texas. The two-part episode of "Oprah's Next Chapter" will air nationally Thursday and Friday, Jan. 17-18, 2013. (AP Photo/Courtesy of Harpo Studios, Inc., George Burns)

Brain-on-a-chip. Dazzling in green and magenta this image shows the nerve fibres (in green) produced by neural stem cells (in magenta) as they grow on a synthetic gel. Captured by a technique known as confocal microscopy, the image is part of research shedding light on how tinkering with the environment can affect the way in which nerve fibres grow. (Photo by Collin Edington and Iris Lee/Massachusetts Institute of Technology/Wellcome Images)

Gus Palmer (Kiowa, at left), side gunner, and Horace Poolaw (Kiowa), aerial photographer, in front of a B-17 Flying Fortress. MacDill Field, Tampa, Florida, ca. 1944. (Photo and caption by 2014 Estate of Horace Poolaw)

“Only the most intrepid urban explorers cross the tattered ruins of the old Iron Curtain to endure the excessive bureaucracy, military paranoia and freezing winds of the East to hunt for the ghosts of an empire. Rebecca Litchfield is one who couldn't resist the haunting allure of the ruins of the Soviet Union”. – Yahoo News. Photo: Hungary, MAV 424 Steam Train. (Photo by Rebecca Bathory)

Shell, which is the replica of the biggest detonated Soviet nuclear bomb AN-602 (Tsar-Bomb), is on display in Moscow, Russia, August 31, 2015. The shell is part of an exhibition organized by the state nuclear corporation Rosatom. (Photo by Maxim Zmeyev/Reuters)

It’s time to start watching for Comet PANSTARRS, one of two comets to get excited about in 2013. Photo: This image provided by NASA shoaws the comet PANSTARRS as seen from Mount Dale, Western Australia on March 5, 2013. According to NASA on March 10, it will make its closest approach to the sun about 28 million miles (45 million kilometers) away. As it continues its nightly trek across the sky, the comet may get lost in the sun's glare but should return and be visible to the naked eye by March 12. (Photo by AP Photo/NASA)