“Daredevil Nik Wallenda became the first person to walk on a tightrope across the Niagara Falls, taking steady, measured steps June 15, 2012 for 1,800 feet across the mist-fogged brink of the roaring falls separating the U.S. and Canada”. (Photo by John Moore/David Duprey/AP Photo)

The Rio de Janeiro Olympics kick off on August 5 for some two weeks of competitive games drawing athletes as well as audiences from around the world. As they prepare to cover the event, Reuters photographers look back on their favourite pictures from past Olympics where they captured the action on the ground as well as the participants' tears and joy that followed. (Photo by Lucy Nicholson/Reuters)

Among the fish populations that could be harmed by the Xayaburi dam in Laos is the critically endangered Mekong giant catfish, considered by the Guinness Book of World Records to be the world’s largest freshwater fish. The fish, which grows to 650 pounds and about 10 feet long, is only found in the Mekong River. It is migratory, moving between downstream habitats in Cambodia upstream to northern Thailand and Laos each year to spawn. Some experts fear the Xayaburi dam could block the migration and drive the giant catfish to extinction. (Photo by Courtesy of Zeb Hogan/University of Nevada, Reno)

«Mignon 2». A.E.G., Berlin, Germany, 1905. Despite its unusual appearance, the Mignon typewriter is of a very clever design, giving a smooth and fast operation for typing. (Photo and caption by Martin Howard/Martin Howard Collection)

Everton fan and legendary fashion photographer Matt Lever has captured the dizzying drama behind the scenes at catwalk shows since 1999. Here: Balmain, Spring/Summer 2011. (Photo by Matt Lever)

7th August 1941: A Soviet sniper targets the enemy with the telescopic sight on his rifle.

A model of the New Horizons spacecraft is seen at a live television program on NASA television celebrating the spacecraft's closest proximity to Pluto, at Johns Hopkins University Applied Physics Laboratory, site of the mission operations center, in Laurel, Maryland, USA, 14 July 2015. At approximately 7:49 am ET (11:49 am GMT), 14 July, New Horizons was scheduled to be as close to Pluto as the spacecraft will get; about 7,800 miles (12,500 kilometers) above the surface, following a journey of more than nine years and three billion miles. This is the first mission to the Pluto System and the Kuiper Belt. (Photo by Michael Reynolds/EPA)

A dog welcomes a volunteer at the “Ping An A Fu” (“Safe and Happy”) Homeless Animals Rescue Center on September 11, 2006 in Nanjing of Jiangsu Province, China. (Photo by China Photos/Getty Images)