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 wax figure of President William Howard Taft is seated in the front seat with his detached head in the back after it was purchased from an auction of the Hall of Presidents Museum, which closed in November, in Gettysburg, Pennsylvania, U.S. January 14, 2017. (Photo by Mark Makela/Reuters)

Former Olympic gymnast Nastia Liukin performs a flip while throwing the ceremonial first pitch during a baseball game between the Los Angeles Angels and the Tampa Bay Rays, Friday, July 14, 2017, in Anaheim, Calif. (Photo by Jae C. Hong/AP Photo)

Masks of Republican presidential candidate Donald Trump (C) and Joaquin "El Chapo" Guzman (2nd L) are seen at Grupo Rev in the Mexican city of Cuernavaca near Mexico City, October 14, 2015. (Photo by Henry Romero/Reuters)

Yakelin Hernandez, 18, poses for a photograph near The Malecon where The Carnival was held, on August 14, 2015. Colorful costumes, dancing, parades and street parties on the Malecon in Havana, Cuba are all part of Havana Carnival 2015 which was held in August. (Photo by Sarah L. Voisin/The Washington Post)

Miss Universe contestants Laurien Angelista, of Curacao, left, Yasmin Verheijen, of the Netherlands, and Kaci Fennell, of Jamaica, walk in the pool during the Yamamay swimsuit runway show, Wednesday, January 14, 2015, in Doral, Fla. The Miss Universe pageant will be held January 25 in Miami. (Photo by Lynne Sladky/AP Photo)

Switzerland's lead Nicole Schwaegli (L) and second Marisa Winkelhausen sweep during their curling round robin game against Japan at the World Women's Curling Championships in Sapporo March 14, 2015. (Photo by Thomas Peter/Reuters)

In this March 14, 2015 photo, tourists take pictures from a viewing area at Iguazu Falls in Brazil. From walkways and bridges, viewers can count 270 water falls almost 100 meters (330 feet) high. (Photo by Jorge Saenz/AP Photo)