Children watch their classmate pour cold water on herself under the watch of a fitness coach at a local kindergarten in Russia's Siberian city of Krasnoyarsk, March 11, 2015. The program, which also involves sports training and sauna usage, has been practiced by the kindergarten for more than 15 years as they believe it has health benefits and keeps the children fit. Children start pouring cold water on themselves outdoors after about three years of training and undergoing medical tests, and the kindergarten is the only one in the region that practices these exercises, according to employees. (Photo by Ilya Naymushin/Reuters)

Internally displaced Syrian children play inside a refugee camp in the Hama countryside, Syria January 1, 2016. (Photo by Ammar Abdullah/Reuters)

Children play amid icebergs on the beach in Nuuk, Greenland, June 5, 2016. (Photo by Alister Doyle/Reuters)

Children play with their pet Hamster at a street in Kochi on March 29, 2021. (Photo by Arun Sankar/AFP Photo)

Children play near an apartment complex on the outskirts of Yangon, Myanmar on July 29, 2019. (Photo by Sai Aung Main/AFP Photo)

A group of children run into a fountain on the South Bank on August 1, 2011 in London, England. Temperatures in the capital reached around 27 degress today and are expected to hit 30 degrees by Wednesday. (Photo by Dan Kitwood/Getty Images)

A family of children share a bath in Japan, circa 1965. (Photo by Three Lions/Hulton Archive/Getty Images)

Father Christmas reading with three young children. (Photo by Spencer Arnold/Getty Images). Circa 1915