Tsar Alexander II (1818–1881) known as “The Liberator” lying in state. He was mortally wounded by an assassination attack in St Petersburg. (Photo by Hulton Archive/Getty Images). March 1881

Children of Indian laborers play on make-shift swings in Amritsar, India, May 12, 2015. (Photo by Narinder Nanu/AFP Photo)

Stones collected and categorised by shape (fish) are seen at the home workshop of Luigi Lineri in Zevio, near Verona, Italy, June 10, 2016. Luigi Lineri's home workshop is covered in stones – tens of thousands of them. They resemble animal heads, human faces and other forms, and the artist and poet believes may have been shaped by prehistoric humans. (Photo by Alessandro Bianchi/Reuters)

Models turned into “humanoid” robots pose on a train at Waterloo Station on October 2, 2016 in London, England for the launch of new Sky Atlantic TV drama Westworld. (Photo by Matt Alexander/PA Wire)

People dressed as zombies participate in a parade for World Zombie Day 2016 in London's West End, Britain on October 9, 2016. (Photo by Splash News and Pictures)

Chinese tourists watch storm clouds moving along the coast towards the city of Sydney, Australia, November 6, 2015. Powerful storms swept across the city on Friday, with the Australian Bureau of Meteorology issuing a warning for severe thunderstorms with large hailstones, heavy rainfall and damaging winds, local media reported. (Photo by David Gray/Reuters)

People ride a motorcycle near Koudoukou Mosque where Pope Francis meets Imam Tidiani Moussa Naibi in Bangui, Central African Republic, November 30, 2015. (Photo by Stefano Rellandini/Reuters)

U.S. Army soldiers with the 1st Battalion, 501st Infantry Regiment deployed to Combat Outpost Sabari, Afghanistan scan their area as they begin a multi-day air assault mission near the Pakistani border of eastern Afghanistan's Khost province May 2, 2012. (Photo by Staff Sgt. Joshua L. DeMotts/U.S. Air Force)