Two guards perform an execution in China, one holding the gun, the other holding a mask over the victim's face. (Photo by General Photographic Agency/Getty Images). Circa 1925

Three prostitutes lean out of a window in Santiago, Chile, in an attempt to entice customers inside, circa 1950. (Photo by Three Lions/Getty Images)

Damaged buildings stand in the rebel-controlled area of Maaret al-Numan in Idlib province, Syria September 6, 2016. (Photo by Ammar Abdullah/Reuters)

A Beija-Flor samba school member performs during the second night of the Carnival parade at the Sambadrome in Rio de Janeiro, Brazil on February 25, 2020. (Photo by Sergio Moraes/Reuters)

Star trails are pictured from a road in Singapore. These astonishing images of night sky are captured by Singapore based photographer Justin Ng. The pictures were taken between November 2013 to January 2014. It show's star trail caused by the earth's rotation and also can be achieved by zooming the DSLR lens inward or outward in small steps using a dedicated motorized zooming device. (Photo by Justin Ng/Barcroft Media)

FaceResearch.org, a site run by two psychologists at the University of Aberdeen in Scotland, features software that can average together faces from thousands of photos. These images purportedly show the average face of women from 40 different nationalities.

Mug shot of William Stanley Moore, 1 May 1925, Central Police Station, Sydney. This picture appears in the Photo Supplement to the NSW Police Gazette, 28 July, 1926 captioned: “Opium dealer. Operates with large quantities of faked opium and cocaine. A wharf labourer; associates with water front thieves and drug traders”. (Photo by NSW Police Forensic Photography Archive, Justice & Police Museum, Histiric Houses Trust of NSW)