An undercover police officer, who had been marching with anti-police demonstrators, aims his gun at protesters after some in the crowd attacked him and his partner in Oakland, California December 10, 2014. Police said more than 100 demonstrators marched in Berkeley, California, which has a history of social activism. Under cloudy skies, turnout was smaller than earlier in the week, when demonstrators in the area threw rocks at police and shut down a major freeway. (Photo by Noah Berger/Reuters)

A frog sits on a leaf and instead of seeing a reflection of itself in the water below, it sees a snail, attached to the bottom of the leaf, in a fish tank in Vietnam. (Photo by Duong Quoc Dinh/Solent Ne/SIPA Press)

Sjinkie Knegt of Netherlands, left, and Park Se-Yeong of South Korea crash out as they compete in a men's 1500m short track speedskating final at the Iceberg Skating Palace during the 2014 Winter Olympics, Monday, February 10, 2014, in Sochi, Russia. (Photo by Bernat Armangue/AP Photo)

A man jokingly poses with a new installation of British graffiti artist Banksy's art in New York, October 20, 2013. (Photo by Carlo Allegri/Reuters)

A masked participant carries a burning matress during the ancient carnival of Zubieta, in the northern Spanish Navarra province on January 30, 2018. The yearly three day festivities, revolving mainly around agriculture and principally sheep hearding, run on the last Sunday, Monday and Tuesday of January where Navarra Valley locals from two villages dress up and participate in a variety of activites as they perform a pilgrimage through each village. (Photo by Ander Gillenea/AFP Photo)

Clowns Perlita and Tapetito, wearing protective gear amid the new coronavirus pandemic, speak with resident Enrique Zeballos as they arrive to disinfect his home free of charge, in El Alto, Bolivia, Friday, September 11, 2020. The lack of traditional employment for the clowns due to the pandemic has led them towards other avenues of making money. But for people with limited income they provide their disinfection services free of charge. (Photo by Juan Karita/AP Photo)

In this May 31, 2016 photo, pieces of watermelon litter the trash area of the Coche public market in Caracas, Venezuela. Staples such as corn flour and cooking oil are subsidized, costing pennies at the strongest of two official exchange rates. But fruit and vegetables have become an unaffordable luxury for many Venezuelan families. (Photo by Fernando Llano/AP Photo)

East Berliners crossing into the West Berlin on November 11, 1989 at the Potsdamer Platz, Germany. (Photo by Kai Wiedenhoefer)