Revelers dance at the Old Settler's Music Festival in Driftwood, Texas, U.S. on April 22, 2017. (Photo by Mohammad Khursheed/Reuters)

Replica of an old traditional Icelandic house from the 1800 with eruption of Iceland's Eyjafjallajökull volcano, 2013. (Photo by Ingólfur Bjargmundsson/Getty Images)

Palestinian boy Mohammad al-Bana, 10, sells mints at a market in Gaza City March 29, 2016. Bana, whose father is unemployed, earns around 10 Shekels ($2.5) per day. The boy starts working after finishing school. He hopes to continue education and become an engineer in the future. (Photo by Mohammed Salem/Reuters)

Fifth-grade students of the General Yermolov Cadet School get prepared before their first military tactical exercise on the ground, which includes radiation resistance classes, forest survival studies and other activities, in Stavropol, Russia, September 10, 2016. Picture taken September 10, 2016. (Photo by Eduard Korniyenko/Reuters)

Student protestors, including one girl with a camera, struggle with soldiers from the Chinese Army, the PLA. Tiananmen Square, 1989. (Photo by Jeff Widener/Associated Press)

“Kids of Sapa”. Four little beautiful Hmong girls from Lao Chai Village, near Sapa, Vietnam. (Photo and caption by Felipe Hanower/National Geographic Traveler Photo Contest)

An Afghan refugee girl stands near her parents' makeshift shelter in a slum on the outskirts of Lahore January 12, 2015. (Photo by Zohra Bensemra/Reuters)