A Brazilian drug gang member nicknamed Pilintra, 26, poses with a gun atop a hill overlooking a slum in Salvador, Bahia State, April 11, 2013. One of Brazil's main tourist destinations and a 2014 World Cup host city, Salvador suffers from an unprecedented wave of violence with an increase of over 250% in the murder rate, according to the Brazilian Center for Latin American Studies (CEBELA). (Photo by Lunae Parracho/Reuters)

A golden huddle by Minqiang Lu, China. Two females and a male golden snub-nosed monkey huddle together to keep warm in the extreme cold. Threatened by forest loss and fragmentation, this endangered species is confined to central China. Restricted to living high up in the temperate forests, these monkeys – here in the Qinling mountains in Shaanxi province – feed mostly in the trees, on leaves, bark, buds and lichen. In heavy wind and snow, Minqiang walked up the mountain carrying his equipment. He stayed for half an hour in temperatures of –10C opposite the tree where the group was huddled before achieving this eye-level composition. (Photo by Minqiang Lu/Wildlife Photographer of the Year)

In this Feb. 17, 2017 photo, surfers walk to La Pampilla beach in Lima, Peru. Night surfing apparently came about in Lima because of a dispute with the capital municipality that in 2015 increased the width of a road that runs along the coast. The surfers protested the construction for months by camping on the asphalted beach area, but in the end the municipality prevailed, with support from the police. At the end of 2016, perhaps to win over the surfers, Lima's mayor set up beach lights that allows for night surfing. (Photo by Rodrigo Abd/AP Photo)

Star Wars actors on the Cantina set at Star Wars Celebration: The Ultimate Fan Experience held at the Anaheim Convention Center on Thursday, April 16, 2015, in Anaheim, Calif. (Photo by Richard Shotwell/Invision/AP Photo)

Ramela Meseljevic, a 7 year-old girl born without both of her hands and one of her legs shorter than the other, writes during classes in the her school in Begov Han, Bosnia and Herzegovina December 2, 2015. International Day of Disabled Persons is observed on December 3 with the theme "Inclusion matters: access and empowerment of people of all abilities". (Photo by Dado Ruvic/Reuters)

“Hippo Chase”. As we approached the camp the Selinda Reserve of northern Botswana our boat passed by a hippo resting in the water. I turned around to look back at the boat's wake and saw the hippo charging after us! The hippo must've been tired from an all-nighter because he was angry. He rose way up out of the water three times trying to chase our boat! He was coming at us with such force that he created a wake of his own. Photo location: Selinda Reserve of northern Botswana. (Photo and caption by Curtis Simmons/National Geographic Photo Contest)

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)

Sugar gliders, Candy and Popcorn, enjoy their favourite food, Nectar, at Wild Life Sydney Zoo on February 14, 2017 in Sydney, Australia. The treat made up of honey, high protein baby cereal and egg yolks is the human equivalent to chocolate to the Sugar Gliders. St. Valentine's Day or the Feast of Saint Valentine began as a celebration of the early Christian Saint Valentinus. From the 18th Century onwards it has steadily transformed into a celebration of romantic love and sentiment in many countries around the world. (Photo by James D. Morgan/Getty Images)