Alex Plunkett, left, and Sean Hart, both of Arlington, Va., join hundreds participating in the annual International Pillow Fight Day on April 5. Massive pillow fights broke out on the Mall in Washington and in cities around the world. (Photo by Marvin Joseph/The Washington Post)

New York City policemen tangled with demonstrators at a subway station on the opening day of the New York World's Fair, April 22, 1964. Youths attempted to stall the train, which was headed from the city to the fairgrounds, as a form of protest on behalf of civil rights for blacks. (Photo by Charles Gorry/AP Photo)

This photo provided by Joan Marcus on August 28, 2015 shows ballerina Misty Copeland in the musical “On the Town” at the Lyric Theatre in New York. Until September 6, 2015 Copeland will play Miss Turnstiles, a love interest for one of three sailors enjoying a few hours of shore leave in 1940s New York. (Photo by Joan Marcus via AP Photo)

“Cub”. In the colony of penguins in South Georgia. (Photo and caption by Ondrej Zaruba/National Geographic Traveler Photo Contest)

ATTENTION! All pictures are presented in high resolution. To see Hi-Res images – just TWICE click on any picture. In other words, click small picture – opens the BIG picture. Click BIG picture – opens VERY BIG picture.

Indian Muslim devotees travel in an auto rickshaw during the Urs festival in Ajmer, India, Thursday, April 23, 2015. Thousands of devotees from different parts of India travel to the shrine of Sufi saint Khwaja Moinuddin Chisht for the annual festival marking the saint's death anniversary. (Photo by Deepak Sharma/AP Photo)

Men are held by Iraqi national security agents, to be interrogated at a checkpoint, as oil fields burn in Qayara, south of Mosul, Iraq, Saturday, November 5, 2016. Islamic State fighters launch counterattacks in the thin strip of territory Iraqi special forces have recaptured in eastern Mosul, highlighting the challenges ahead as the battle moves into more densely populated neighborhoods where coalition air power must be used more selectively. (Photo by Felipe Dana/AP Photo)

Muslim women light candles during the “EarthHour” in Jakarta, Indonesia, on March 23, 2013. Hundreds of people observed the global event that encourages people to turn off their lights for 60 minutes. (Photo by Dita Alangkara/Associated Press)

“Fly cap for a vine snake”. A fly lands on the head of a vine snake in the Choco of Colombia. (Photo and caption by Robin Moore/National Geographic Traveler Photo Contest)

ATTENTION! All pictures are presented in high resolution. To see Hi-Res images – just TWICE click on any picture. In other words, click small picture – opens the BIG picture. Click BIG picture – opens VERY BIG picture.