Young children at a Bristol, Great Britain health centre unsure of the benefits of sun-lamps and the special glasses that must be worn, July 1948. The health centre was part of the newly introduced free National Health Service. (Photo by Popperfoto/Getty Images)

Campers set structures on fire in preparation of the Army Corp's 2pm deadline to leave the Oceti Sakowin protest camp on February 22, 2017 in Cannon Ball, North Dakota. Activists and protesters have occupied the Standing Rock Sioux reservation for months in opposotion to the completion of the Dakota Access Pipeline. (Photo by Stephen Yang/Getty Images)

A worker carries a basket of fish, at a wholesale fish market, on the outskirts of Kolkata, March 15, 2017. (Photo by Rupak De Chowdhuri/Reuters)

A woman carries earthen pots to fill them with drinking water on a hot summer day, on the outskirts of Ajmer, Rajasthan, India April 25, 2017. (Photo by Himanshu Sharma/Reuters)

People enjoying the races on a wet day at Chester Racecourse on May 12, 2017 in Chester, England. (Photo by Alan Crowhurst/Getty Images)

Female labourers wearing helmets take a break from laying underground electricity cables in Ahmedabad, India, March 7, 2016. (Photo by Amit Dave/Reuters)

Partially demolished houses stand in the Vila Autodromo slum with the Rio 2016 Olympic Park in the background in Rio de Janeiro, Brazil, February 25, 2016. (Photo by Ricardo Moraes/Reuters)

A man dressed as the “Star Wars” character Darth Vader sits on a bench in central Lviv, Ukraine, November 24, 2016. (Photo by Gleb Garanich/Reuters)