A couple looks at their flooded street from behind their home's window in La Plata, in Argentina's Buenos Aires province, where at least 35 people were killed by flooding overnight, on April 3, 2013. (Photo by Natacha Pisarenko/Associated Press)

People ride a Ferris wheel as fireworks illuminate the sky over Edinburgh, Scotland. (Photo by David Cheskin/Press Association)

Marine biologist Simon Pierce, who studies whale sharks, happened to be in the right place at the right time to capture amazing photo off Cancun, Mexico. (Photo by Simon Pierce/Mercury Press/Caters News)

“Don't Leave Any Food On Your Plate”. The giraffes at Nairobi's Giraffe Manor are totally at home with humans. They will eat out of your hand, or even off your plate. Photo location: Giraffe Manor, Nairobi, Kenya. (Photo and caption by Gavin Werbeloff/National Geographic Photo Contest)

A model showcases designs on the runway at MGPIN 2015 Mao Geping Makeup Trends Launch show during Mercedes-Benz China Fashion Week Spring/Summer 2015 at Beijing Hotel on October 27, 2014 in Beijing, China. (Photo by Feng Li/Getty Images)

A visitor takes in a view of the downtown district from Twin Peaks on Friday, January 9, 2015, in San Francisco. (Photo by Marcio Jose Sanchez/AP Photo)

In this October 15, 2014 file photo, Katsu Nakamura, sky division manager for Yamaha USA, moves the RMax unmanned helicopter into position before a demonstration of its aerial application capabilities at the University of California, Davis' Oakville Station test vineyard in Oakville, Calif. Researchers at UC Davis have been studying the effectiveness of the drone's ability for spraying pest control and nutritional materials on the test vineyard in California's Napa Valley. (Photo by Rich Pedroncelli/AP Photo)

A replica of pre-historic drawings showing horses, rhinoceros and aurochs is seen on a wall during a press visit at the site of the Cavern of Pont-d'Arc project in Vallon Pont d'Arc April 8, 2015. The Cavern of Pont-d'Arc project is a replica of the pre-historic Decorated Cave of Pont-d'Arc known as Grotte Chauvet, in Vallon Pont-d'Arc in the Ardeche region, containing the world's earliest known art which was recently named a UNESCO World Heritage site. The facsimile cavern, which condenses some 8000m² of the original site into 3000m², will display faithful reproductions of paintings and engravings and will be inaugurated on April 10 and will open to the public on April 25. (Photo by Robert Pratta/Reuters)