Juno, a Beluga whale, greets a young viewer at the Mystic aquarium in Connecticut, USA on December 5, 2015. (Photo by Tim Clayton/Corbis)

Young U.S. visitors pose for a photograph next to a vintage car in Havana March 16, 2016. (Photo by Ueslei Marcelino/Reuters)

Young female Ibex on the fork of Disteis (2,200 m), near the top of the Jof di Montasio (Friuli, Italy). (Photo by Stefano Zocca)

Young man making the O.K. sign. (Photo by George Marks/Retrofile/Getty Images). Circa 1950s

Students celebrate their A-level results at King Edward VI High School for Girls in Birmingham, England on August 18, 2016. The proportion of top grades achieved by A-level students across the UK has fallen for a fifth year in a row, and girls have caught up with boys in attaining A* grades. (Photo by Joe Giddens/PA Wire)

A young Free Syrian Army fighter holds a rifle in Haresta neighbourhood of Damascus January 16, 2013. (Photo by Goran Tomasevic/Reuters)

Attendees at Wizard World Comic Con walk through hallways in Chicago, Illinois, United States, August 22, 2015. (Photo by Jim Young/Reuters)

Young gymnasts practice pull-up on a bar at a gymnasium of a sports school in Jiaxing, Zhejiang province April 11, 2015. (Photo by William Hong/Reuters)