A young girls holds a ballot during the Greek referendum in Athens on July 5, 2015. Greek voters headed to the polls today to vote in a historic, tightly fought referendum on whether to accept worsening austerity in exchange for more bailout funds, in a gamble that could see it crash out of the euro. (Photo by Aris Messinis/AFP Photo)

Cave Diver, Anhumas Abyss, Bonito, Brazil: The Anhumas Abyss is an underground cavern with a crystal-clear lake below, more than 260 feet (79 m) deep. A visitor must enter through a narrow opening at the top of the chamber and rappel into the cave. Snorkeling and scuba diving in the lake reveal amazing scenery. Distinctive, conical limestone stalagmites and stalactites occupy the lake and the surrounding area, some reaching 65 feet (20 m) high. (Photo by Marcio Cabral/Nature’s Best Photography Awards 2017)

Felipe Dana discovered photography at age 15 when he started working as an assistant for event and commercial photographers. At the close of 2009, he decided to focus his career solely on photojournalism. Dana has focused his work on documenting the consequences of social changes in slums due to upcoming major sports events scheduled for 2014 and 2016 in Rio de Janeiro, where he currently lives and works as a staff photographer for The Associated Press. Photo: A model wears a creation from the Triya summer collection during Fashion Rio in Rio de Janeiro, Brazil, Friday, April 19, 2013. (Photo by Felipe Dana/AP Photo)

Heidi Klum attends the Heidi Klum's 16th Annual Halloween Party sponsored by GSN's Hellevator And SVEDKA Vodka At LAVO New York on October 31, 2015 in New York City. (Photo by Mike Coppola/Getty Images for Heidi Klum)

Friends and relatives mourn by the coffin during the wake for Florjohn Cruz, who was killed in a police drugs buy-bust operation, in Manila, Philippines late October 20, 2016. (Photo by Damir Sagolj/Reuters)

A man cries in a graveyard during the funeral of Nasser Ali Afglio, a young Libyan rebel killed during battle with government troops loyal to Libyan ruler Moammar Gaddafi April 19, 2011 in Misrata, Libya. The graveyard where Nasser was buried has hundreds of simple concrete graves; many dozens are those that have been killed during the last two months of fighting in the besieged town. Thousands of civilians are trapped in Misrata as fighting continues between Libyan government forces that have surrounded the city and anti-government rebels there. (Photo by Chris Hondros/Getty Images)

A Panasonic Toughpad is displayed during a press event at The Venetian for the 2012 International Consumer Electronics Show (CES) January 9, 2012 in Las Vegas, Nevada. CES, the world's largest annual consumer technology trade show, runs from January 10-13 and is expected to feature 2,700 exhibitors showing off their latest products and services to about 140,000 attendees. (Photo by Ethan Miller/Getty Images)

Japanese researchers have sparked hopes of finding a cure for human baldness after successfully growing hair on hairless mice by implanting follicles created from stem cells, Agence France Presse reports. A picture taken on April 13, 2012 and released by the Tsuji Lab Research Institute for Science and Technology of the Tokyo University of Science shows a hairless mouse with black hair on its back at the laboratory in Noda, Chiba Prefecture. (Photo by Tokyo University of Science via AFP)