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)

Ten-year-old Macy Friday, front left, reacts as she looks back at her family after meeting Hillary Clinton, front right, as she campaigns for U.S. Sen. Mark Udall, D-Colo., back, during a stop in the newly-renovated Union Station in Denver on Monday, October 13, 2014. Clinton appeared at an event to raise money for Udall's current re-election campaign and then headed to Las Vegas for another appearance on Monday night. (Photo by David Zalubowski/AP Photo)

The car driven by Scott Dixon, of New Zealand, goes over the top of Jay Howard, of England, in the first turn during the running of the Indianapolis 500 auto race at Indianapolis Motor Speedway, Sunday, May 28, 2017, in Indianapolis. (Photo by Marty Seppala/AP Photo)

People try to get a roast chicken at the first Costco outlet in China, on the stores opening day in Shanghai on August 27, 2019. China has proved a brutal battleground for overseas food retailers in recent years, with many failing to understand consumer habits and tastes as well as local competitors building a stronger presence. (Photo by Hector Retamal/AFP Photo)

Japanese college students look at cheerleaders during a job-hunting rally in Tokyo January 29, 2014. According to the rally organizers, about 1,500 students from vocational schools attend the rally to boost their morale ahead of their job hunt. (Photo by Yuya Shino/Reuters)

An India Christian devotee reenacts the sufferings of Jesus Christ on the occasion of Good Friday in Mumbai, India, Friday, March 29, 2013. Christians all over the world are marking Good Friday, the day when Christ was crucified. (Photo by Rajanish Kakade/AP Photo)

People dance in a park on a foggy day in Huai'an, Jiangsu province, China October 10, 2017. (Photo by Reuters/China Stringer Network)

The Tianzi Hotel with the shape of Chinese deities Fu, Lu and Shou is pictured on November 20, 2017 in Langfang, Hebei Province of China. The 41.6-meter-tall Tianzi Hotel has an exterior of Chinese Sanxing, whose names are Fu, Lu and Shou with the qualities of prosperity, status and longevity in traditional Chinese culture, in Langfang city. (Photo by VCG/VCG via Getty Images)