Wedges of an orange generate enough current and electrical juice – 3.5 volts – to power an LED. The fruit’s citric acid helps electrons flow from galvanized nails to copper wire in this 14-hour exposure. This image was published in September’s Visions of Earth, a trio of photos that appear in each issue of National Geographic. (Photo by Caleb Charland/National Geographic)

“March 19, 2012 was the first rehearsal for the Victory Day Parade at the training ground in Alabino (near Moscow, Moscow Military District). Since the end of February troops and vehicles from various units and formations of the Armed Forces began arriving to Alabino training ground. The first rehearsal included only military vehicles. During the ride the average speed of vehicles is 12 km/h, the distance depending on the type of vehicle from 12 to 15 meters”. – Vitaly Kuzmin

British comedian and director Charles Chaplin (1889–1977) and actress Paulette Goddard (1911–1990), to whom he was married for seven years, star in the comedy “Modern Times”, directed by Chaplin himself. (Photo by Hulton Archive/Getty Images). 1936

Andrea Petkovic of Germany in action against Sara Errani of Italy during day one of the Mutua Madrid Open tennis tournament at the Caja Magica on May 3, 2014 in Madrid, Spain. (Photo by Julian Finney/Getty Images)

“Weapons Instructor”, 2012. It’s a well known fact that the IDF trains some of the best soldiers in the world, but at the source of every good soldier lies an exceptional instructor – and that’s where Cpl. Daniella Stepanoe steps in. She travels from base to base training everyone from paratroopers to elite special forces units in the use of their weapons. (Photo by Israel Defense Forces)

Waura Indians wrestle during this year's “quarup”, a ritual held over several days to honour in death a person of great importance to them, in Xingu National Park, Mato Grosso State, Brazil August 25, 2013. (Photo by Ueslei Marcelino/Reuters)

A Syrian migrant family enters Hungary at the border with Serbia near Roszke, Hungary August 28, 2015. As Europe struggles with its worst migrant crisis since World War II, Hungary has become, like Italy and Greece, a “frontline” state. So far this year, police say around 141,500 migrants have been intercepted crossing into Hungary, mostly from neighbouring Serbia. (Photo by Bernadett Szabo/Reuters)

Hotel guides jump as they pose for pictures outside the Great Hall of the People during the opening session of the National People's Congress (NPC) in Beijing, China, March 5, 2016. (Photo by Aly Song/Reuters)