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)

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)

Highly commended, mammals: Gelada after the storm – Marco Gaiotti (Italy). “Gelada baboons are the only monkey species in the world that feed on grasses. They are native to the tableland of Ethiopia. Every morning large family groups wander from their sleeping places in the steep rock face, up to 1,000 metres high, to the feeding grounds at the tablelands. This image clearly depicts their feeding strategy: they pull out bunches of grass, sort the stalks and then lift them to their mouth. This shot was taken towards the end of the rainy season after a heavy storm”. (Photo by Marco Gaiotti/2019 GDT European Wildlife Photographer of the Year)

“The Net thrower”. The fisherman are conducting activities on Situgunung Lake. Photo location: Situgunung lake, Sukabumi, West Java, Indonesia. (Photo and caption by Dody Kusuma/National Geographic Photo Contest)

An exhibitor takes a photo with a Huawei Mate 10 Pro during the 2018 CES in Las Vegas, Nevada, U.S. January 9, 2018. CES, the world's largest annual consumer technology trade show, runs through January 12 and features about 3,900 exhibitors showing off their latest products and services to more than 170,000 attendees. (Photo by Steve Marcus/Reuters)

French firemen wearing chemical protective suits take part in a mock chemical attack exercise at the Geoffroy Guichard stadium in Saint-Etienne, France, April 4, 2016 in preparation of security measures for the UEFA 2016 European Championship. (Photo by Robert Pratta/Reuters)

A giant Iron Man statue stands next to a replica Sphinx in Chuzhou, Anhui Province, China on February 21, 2017. (Photo by Sipa Asia/Rex Features/Shutterstock)

A woman counts her money as she sells flowers ahead of International Women's Day in central Kiev, Ukraine on March 7, 2019. (Photo by Gleb Garanich/Reuters)