Japanese chorus girls appear to be drilling in military tactics atop their theater building as they perform salutes, June 30, 1937. The officer is from the Japanese regular army and says the girls display more rhythm in their drills than do the regular troops. (Photo by AP Photo)

Afghan girl athletes perform Wushu on the top of a hill in Kabul, capital of Afghanistan, January 18, 2017. In the conservative Afghan society where people especially in the countryside deeply believe in the old traditions and don't allow their girls and female members of the family to go out of home, exercising sport in open is extremely risky, but a group of girls are broken the taboo and exercising Wushu on a hilltop where the temperature is minus 2 Celsius degrees. (Photo by Rahmat Alizadah/Xinhua/Barcroft Images)

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)

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

A young boy lifts heavy bricks as he works at brick factory around Kathmandu valley. (Photo by Narendra Shrestha/EPA)

A young Shiite Muslim child participates in a Muharram procession in Ahmadabad, India, Sunday, October 9, 2016. (Photo by Ajit Solanki/AP Photo)

Two young women embrace in bed together, both wearing white lace underwear. (Photo by Popperfoto/Getty Images)