At the beginning of the 20th century, Edward S. Curtis set out to document what he saw as a disappearing race: the Native American. From 1907 to 1930, Curtis took more than 2,000 photos of 80 tribes stretching from the Great Plains to the Pacific Northwest and Alaska. He then published and sold these photos, along with narrative text, in 20 volumes of work known as “The North American Indian”. It is one of the most significant collections of its kind, “probably the most important photographic document of its age and its topic,” said Jeffrey Garrett, associate university librarian for Special Libraries at Northwestern University. (Photo by Edward S. Curtis)

Reuters photographers Carlos Barria and Bobby Yip photographed protestors and details of life on the barricades, asking demonstrators what their role was in the movement, and what they wanted to happen. Here: Crystal, 15, a part-time boutique sales assistant, poses on Nathan Road in Mongkok shopping district in Hong Kong October 7, 2014. Holding a walkie talkie for fast communication with other supporters, Crystal said, “I am not demanding Chief Executive Leung Chun-ying to quit, but (want) to protect protesters from being threatened badly by opponents and the police”. (Photo by Bobby Yip/Reuters)

A street in the Cuban capital, Havana, is home to 12 sets of twins, ranging from toddlers to senior citizens. Some say it could be something in the water. Others point to a tree with mystical significance for locals. And maybe it's just chance. Photo: In this September 29, 2013 photo, nine-year-old twin sisters Camila, left, and Carla Rodriguez pose for a portrait along their street in Havana, Cuba. 12 sets of twins live along two consecutive blocks in western Havana, ranging in age from newborns to senior citizens. “We love living on this block because we have twin friends”, said Carla. (Photo by Ramon Espinosa/AP Photo)

An Indian Sikh Nihang, or warrior, performs Gatka martial arts skills during a procession at the Golden Temple in Amritsar on January 6, 2014, as part of birth anniversary celebrations of Guru Gobind Singh. The birth anniversary of Guru Gobind Singh, the tenth Sikh guru, is marked on January 6. (Photo by Narinder Nanu/AFP Photo)

A Russian prisoner eating bread. (Photo by Hulton Archive/Getty Images). Finland, circa 1940

“The Spanish Civil War (The Crusade among Nationalists, Fourth Carlist War among Carlists, The Rebellion or Uprising among Republicans) was a major conflict fought in Spain from 17 July 1936 to 1 April 1939. An estimated total of 500,000 people lost their lives as a consequence of the War”. – Wikipedia

Photo: Women were among the Republican combatants during the Spanish Civil War. (Photo by Fox Photos/Getty Images). 1936

“The Tokyo Metropolitan Central Wholesale Market, commonly known as the Tsukiji Market, is the biggest wholesale fish and seafood market in the world and also one of the largest wholesale food markets of any kind. The market is located in Tsukiji in central Tokyo, and is a major attraction for foreign visitors”. – Wikipedia

Photo: A 232kg blue-fin tuna is displayed during the new year's first auction at the Tsukiji fish market on January 5, 2010 in Tokyo, Japan. (Photo by Koichi Kamoshida/Getty Images)

Shoppers walk down stairs featuring a five-metre-high reproduction of Vincent van Gogh's signature painting “Sunflowers”, at the entrance to Ocean Terminal in Hong Kong July 15, 2013. A premium three-dimensional reproduction of works of Van Gogh, the RELIEVO collection, approved by the curators of the Van Gogh Museum in Amsterdam, is on display at a gallery inside Harbour City shopping mall attached to the terminal. (Photo by Bobby Yip/Reuters)