A walruses at Hagenbeck Zoo in Hamburg, Germany on July, 7, 2015. (Photo by Werner Struss/Startraks action)

A man makes a mud oven to be used for baking bread at a workshop in Najaf, south of Baghdad, July 23, 2015. (Photo by Alaa Al-Marjani/Reuters)

Girls ride on a donkey cart with grass for animals on the outside of Nangarhar province, Afghanistan May 19, 2015. (Photo by Reuters/Parwiz)

Competitors release their hens during the World Championship Hen Racing Championships in Bonsall, Britain August 1, 2015. (Photo by Darren Staples/Reuters)

An incredible clear-air lightning display from storms to the east of Noonamah, just outside Darwin on April 6, 2015. (Photo by Jacci Ingham/The Guardian)

Children play in front of a brick factory on the outskirts of the northern Myanmar city of Mandalay on December 14, 2015. (Photo by Phyo Hein Kyaw/AFP Photo)

A prototype Rollkers transportation device is displayed during a press event at the Mandalay Bay Convention Center for the 2015 International CES on January 4, 2015 in Las Vegas, Nevada. The product is not a skate; it balances for you and when you place it on the bottom of your shoe, it gives you the ability for faster transportation based on walking. The balance CES, the world's largest annual consumer technology trade show, runs from January 6-9 and is expected to feature 3,600 exhibitors showing off their latest products and services to about 150,000 attendees. (Photo by Ethan Miller/Getty Images)

A girl dances in front of the digital art installation “Light in Dark” created by teamLab, a collaborative of Japanese digital artists, during a special exhibition of “Shake! Art Exhibition! and Learn and Play! teamLab Future Park” at National Museum of Emerging Science and Innovation (or Miraikan) in Tokyo, Japan, 19 January 2015. The exhibition is held through 01 March 2015. (Photo by Kimimasa Mayama/EPA)