Some of London's telephone operators and engineers, trying out their gas masks at the anti-gas civilian training centre in Gloucester, where they were taught how to deal with gas attacks. (Photo by Harry Todd/Fox Photos/Getty Images). 13th February 1937

A tiger cub has a short chat with a chimp. (Photo by Ian Tyas/Keystone Features/Getty Images). 27th November 1979

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

Bonbibi, Treehouse Point, Fall City, WA. The Bonbibi is balanced on two steel yokes. The yokes spread out the load and allow for tree growth and movement in the wind. A small deck hangs from the beams below and uses the treehouse itself to shelter guests. (Photo by Pete Nelson)

This photo taken on December 10, 2023 shows female members of the Mandalay People's Defense Forces (MDY-PDF) heading to the frontline amid clashes with the Myanmar military in northern Shan State. In the hills of northern Myanmar young women fly combat drones, treat wounded comrades and patrol the frontlines, new roles in the battle to overthrow the military junta. (Photo by AFP Photo/Stringer)

Technicians check a CRH high-speed train at Shanghai Hongqiao High-speed train base on December 28, 2011 in Shanghai, China. China's railway stations have started today to sell tickets for the 2012 Spring Festival travel season scheduled to run between January 8th and February 16th, centred around the Chinese New Year which this year falls on January 23rd. (Photo by ChinaFotoPress/Getty Images)

Sеx worker Moira Mona wears a mask at her studio where she creates videos near Amsterdam, Netherlands on June 30, 2020. (Photo by Piroschka van de Wouw/Reuters)

Visitors browse in the starry Art Museum. Shanghai, China, May 13, 2020. The exhibition hall uses a large number of mirror devices, combined with the layout of acousto-optic, to create a visual scene and spatial effect. (Photo by Costfoto/Barcroft Media via Getty Images)