Workers lay railway track in a tunnel of the Crossrail project in Stepney, east London, Britain, November 16, 2016. Crossrail, which is Europe's largest construction project, is a railway link which will connect outlying areas to the east and west of London with tunnels under the centre of the capital. (Photo by Stefan Wermuth/Reuters)

In this Tuesday, June 18, 2013 photo, Zita, a liger – half-lioness, half-tiger – carries her one month-old liliger cub in the Novosibirsk Zoo. The cub's father is a lion, Sam. (Photo by Ilnar Salakhiev/AP Photo)

This photo taken on April 25, 2015 shows a pet male monkey named “JK” (R) and his partner “Shaki” (L) eating dinner at a restaurant in Kuala Lumpur. Jamil, a 45-year single Malaysian man, has unusual pets – two macaque monkeys. JK and Shaki, both nine years old, usually ride with Jamil on his motorcycle and they often have dinner together in public restaurants, drawing instant public awe. (Photo by Mohd Rasfan/AFP Photo)

A woman reacts as she uses a selfie stick to take a photo of herself at Tiananmen Square in Beijing, China, Thursday, April 30, 2015. Selfie sticks are gaining popular in China, and many people are using them at popular tourist destinations. (Photo by Andy Wong/AP Photo)

In this Saturday, July 4, 2015 photo, Israeli and Russian members of knight clubs cook their breakfast before the reenactment of the Battle of Hattin in Lavi Forest, northern Israel. About a third of the participants arrived with their elaborate gear from Russia. The project is supported by the Lower Galilee Regional Council. (Photo by Oded Balilty/AP Photo)

This March 1, 2013 file photo shows a worker selecting cigars at the H. Upmann cigar factory, where people can take tours as part of the 15th annual Cigar Festival in Havana, Cuba. (Photo by Ramon Espinosa/AP Photo)

In this Sunday, May 22, 2016 photo, contestants in the first Miss Trans Israel beauty pageant gather for rehearsal in Tel Aviv, Israel. The pageant will be held at HaBima, Israel's national theater, in Tel Aviv on Friday. Tel Aviv has emerged as one of the world's most LGBT-friendly travel destinations, standing in sharp contrast to most of the rest of the Middle East, where gays can face persecution. (Photo by Oded Balilty/AP Photo)

The Vietnam Slide Project was created by photo editor Kendra Rennick, who began collecting photo slides after a close friend lost her father, a Vietnam veteran. Her friend found a box of slides that her father had taken while in Vietnam and from there Rennick has continued to collect photographs that Vietnam veterans took during their tours of duty. Here: A photo taken from the collection of D.Thornton, who served in the First Air Cavalry division of the United States Army. (Photo by D.Thornton/The Vietnam Slide Project)