A polar bear fast asleep at London Zoo. (Photo by Fox Photos/Getty Images). 1961

A baby bush-baby in a set of scales at London Zoo shortly after birth. (Photo by Fox Photos/Getty Images). 10th August 1938

Studio stack: Rabbit? Acanthocinus aedilis, Cerambycidae, A female Timberman (Timbermam perhaps?). Stacked from 216 exposures in Zerene Stacker (PMAX). (Photo by John Hallmén). P.S. All pictures are presented in high resolution.

An Indian Brahmin and his family. (Photo by Hulton Archive/Getty Images). Circa 1890

A three wheeled “cabin” scooter manufactured by German aircraft engineers Messerschmitt & Co at factories in Regensburg. (Photo by Hans Enzwieser/BIPs/Getty Images). 1955

In this March 7, 1991 file photo, a U.S. Marine patrol walks across the charred oil landscape near a burning well during perimeter security patrol near Kuwait City. Twenty five years after the first U.S. Marines swept across the border into Kuwait in the 1991 Gulf War, American forces find themselves battling the extremist Islamic State group, born out of al-Qaida, in the splintered territories of Iraq and Syria. The Arab allies that joined the 1991 coalition are fighting their own conflicts both at home and abroad, as Iran vies for greater regional power following a nuclear deal with world powers. (Photo by John Gaps III/AP Photo)

A cat walks in front of the body of a man killed by unknown gunmen in Manila, Philippines early October 18, 2016. A sign on a cardboard found near the body reads, “Pusher Ako, Wag Tularan”, which translates to “I am a (drug) pusher, don't be like me”. (Photo by Damir Sagolj/Reuters)

In this photo taken on Friday, July 14, 2017, a student at a paramilitary camp for children calls the rank to attention outside Kiev, Ukraine. As the deadly conflict in eastern Ukraine entered its third year, some parents in Ukraine are anxious to make sure their children are ready to fight it, instead of swimming and playing volleyball. (Photo by Efrem Lukatsky/AP Photo)