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 reveller from Uniao da Ilha samba school performs during the second night of the carnival parade at the Sambadrome in Rio de Janeiro, Brazil February 27, 2017. (Photo by Pilar Olivares/Reuters)

A model Cindy Bruna presents a creation on a giant catwalk installed on a barge on the Seine River during a public event organized by French cosmetics group L'Oreal as part of Paris Fashion Week, France, September 30, 2018. (Photo by Stephane Mahe/Reuters)

Men pull with a rope the body of an Islamic State fighter before burying him near Karamah, south of Mosul, Iraq November 11, 2016. (Photo by Goran Tomasevic/Reuters)

Stuart Craig of Washington tries out a Sig Sauer 1911 model Scorpion pistol at the Sig Sauer booth at the National Shooting Sports Foundation's 34th annual Shooting, Hunting, Outdoor Trade (SHOT) Show at the Sands Expo and Convention Center January 17, 2012 in Las Vegas, Nevada. The SHOT Show is the largest annual gathering of shooting professionals with more than 1,600 exhibitors and 30,000 attendees expected. (Photo by Ethan Miller/Getty Images)

Bottles of vintage cognac, with a royal warrant stamp, are seen in storage inside Berry Bros and Rudd wine merchants in central London, Britain, August 21, 2015. Berry Bros. & Rudd, which started as grocers over 300 years ago in St. James's, central London, has two royal warrants. Every year Queen Elizabeth grants about 20 royal warrants, the gold emblem of the British monarchy, in a practice dating back to medieval times. The warrant holders can display the certificate and use the royal coat of arms in their marketing. The warrants lasting five years can help businesses break into new markets overseas, using their role as supplier to the royal family as a gauge of quality. On September 9, Queen Elizabeth will overtake Queen Victoria as Britain's longest-serving monarch. (Photo by Toby Melville/Reuters)

Prince Charles, Prince of Wales (R) and Camilla, Duchess of Cornwall (L) visit Seppeltsfield Winery in Barossa Valley, Australia, 10 November 2015. The royal couple are on a 12-day tour visiting seven regions in New Zealand and three states and one territory in Australia. (Photo by Daniel Kalisz/EPA)

A three-seater Toyota Kikai concept car is displayed during the 2016 CES trade show in Las Vegas, Nevada January 8, 2016. (Photo by Steve Marcus/Reuters)