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)

A competitor wearing a kilt and standing on a barrel throws a bowling ball between her legs during the “Brigaball” contest at the annual Bundanoon Highland Gathering, showcasing traditional Scottish events, held in the town of Bundanoon, located southwest of Sydney, April 9, 2016. (Photo by David Gray/Reuters)

Republican Presidential Candidate Donald Trump kisses his wife Melania Trump as he introduces her during first day of the Republican National Convention in Cleveland, Monday, July 18, 2016. (Photo by Matt Rourke/AP Photo)

A woman uses a tree branch to fight a fire on the road leading to the village of Parada, near Mortagua, northern Portugal, Thursday, August 11 2016. Firefighters in Portugal are battling multiple blazes fed by brush in a hot, dry summer for a sixth straight day. Major fires have also been raging in northwestern Spain and southern France. (Photo by Sergio Azenha/AP Photo)

An “asparagus eating contest” made of asparagus and carved pumpkins is on display on the sidelines of the Giant Vegetable Competition in Klaistow, northeastern Germany, on September 20, 2015. The vegetable giants compete in seven categories. (Photo by Bernd Settnik/AFP Photo)

Droid BB-8 arrives at the world premiere of the film “Star Wars: The Force Awakens” in Hollywood, California, December 14, 2015. (Photo by Mario Anzuoni/Reuters)

A woman offers prayers by a road as a rickshaw puller transports passengers in Kolkata October 28, 2014. (Photo by Rupak De Chowdhuri/Reuters)

A Felix the Cat balloon and other parade floats and balloons are led down Broadway during the annual Macy's Thanksgiving Day Parade; ca. 1900s, Broadway, Manhattan, New York City, New York State, USA. (Photo by Underwood & Underwood/Corbis)