A dejected German Grenadier carrying a machine gun on his shoulder in front of a building on fire during the German retreat in Russia. (Photo by Keystone/Getty Images). 1944

Eight-year-old Niu Dongfang trains at the No. 2 Beijing Shuangqiao School January 13, 2005 in Beijing, China. Most of students in the gymnastics school have to study more than five years from as young as age six before they become athletes. (Photo by Guang Niu/Getty Images)

A girl laughs while unloading her boat of produce at a market in Ganvie on January 6, 2012 in Cotonou, Benin. Often called the Venice of Africa, Ganvie is a stilted fishing village on Lake Nokoue, near Cotonou in Benin, the largest such village in Africa, and home to approximately 20,000 residents. (Photo by Dan Kitwood/Getty Images)

With their wings at full length, these beautiful golden eagles soar through the skies in a glorious training session to hunt their prey. Others sit on the arms of their owners and trainers. Batzaya Choijiljav, 41, from Mongolia has taken these magnificent pictures at the annual traditional Kazakhs festival, October 2015. (Photo by Batzaya Choijiljav/Caters News)

Swimmers prepare to take part in the annual Christmas Day Peter Pan Cup handicap race in the Serpentine River, in Hyde Park, London, December 25, 2015. (Photo by Andrew Winning/Reuters)

A baby is baptised during a mass baptism ceremony on Epiphany day in Tbilisi, January 19, 2015. About 1000 children were baptised by the Georgian Orthodox church during the 38th mass baptism ceremony at the country's main cathedral Holy Trinity. (Photo by David Mdzinarishvili/Reuters)

The Vietnam Slide Project was created by photo editor Kendra Rennick, who began collecting photo slides after a close friend lost her father, a Vietnam veteran. Her friend found a box of slides that her father had taken while in Vietnam and from there Rennick has continued to collect photographs that Vietnam veterans took during their tours of duty. Here: A photo taken from the collection of D.Thornton, who served in the First Air Cavalry division of the United States Army. (Photo by D.Thornton/The Vietnam Slide Project)

Ada Wood, 10, perches on one of Castlerigg’s 38 stones during the summer solstice at Castlerigg stone circle in Cumbria, Britain, on June 21, 2016. (Photo by Christopher Thomond/The Guardian)