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)

Russian pop art photographer Sergey Chilikov captures a nation liberated from the social oppression of late-era Soviet rule – at parties, in the streets, and bouncing high. His exhibition, Photoprovocations, will be at Photo London, 19-22 May. Here: Yoshkar-Ola, Matrosova Street (1995). (Photo by Sergey Chilikov)

An invited guest enjoys a private listening experience of a test unit of the Sennheiser HE 1 sound system, which is expected to retail for about S$77370 ($55000), in a hotel suite during the CanJam headphone and personal audio expo in Singapore February 21, 2016. (Photo by Edgar Su/Reuters)

On Dale A. Browne’s first trip to Yellowstone, he “got the best shot” he’d ever taken after chasing this weasel for 30 minutes. The trip for the 58-year-old from Manassas, Va., was a gift from his wife and an opportunity to improve his photography skills with the help of guide and professional photographer Tom Murphy. (Murphy did not assist in the taking of this photo). (Photo by Dale A. Browne)

Radin the Sunda pangolin hitches a ride on Nita as their keeper looks on. The elusive and nocturnal Sunda pangolin produces only one or two offspring a year and Radin is the third pangolin baby born in Night Safari since 2011. (Photo by Wildlife Reserves Singapore)

Women joke around as they pose for photographs in front of a large dragon made of flowers at the Sentosa Flowers festival on January 22, 2012 on Sentosa Island, Singapore. (Photo by Chris McGrath/Getty Images)

Family of passengers onboard AirAsia flight QZ8501 react at a waiting area in Juanda International Airport, Surabaya December 28, 2014. Indonesia's air force was searching for the AirAsia plane carrying 162 people that went missing on Sunday after the pilots asked to change course to avoid bad weather during a flight from the Indonesian city of Surabaya to Singapore. The Airbus 320-200 lost contact with Jakarta air traffic control at 6:17 a.m. (23:17 GMT), officials said. (Photo by Reuters/Beawiharta)

Images created with Post-it notes are seen in the windows of offices at 75 Varick Street in lower Manhattan, New York, U.S., May 18, 2016, where advertising agencies and other companies have started what is being called a “Post-it note art war” with employees creating colorful images in their windows with Post-it notes. (Photo by Mike Segar/Reuters)