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 Hindu devotee lies on a road as she worships the Sun god during the religious festival of Chhath Puja in Kolkata, India October 26, 2017. (Photo by Rupak De Chowdhuri/Reuters)

Audience take photos of a model presenting a creation by Greek designer Dimitrios Ordoulidis during the 10th Athens Exclusive Fashion Week in Athens, Greece, October 22, 2016. (Photo by Alkis Konstantinidis/Reuters)

Breath of an Arctic fox by Marco Gaiotti, Italy. Marco was watching this little Arctic fox as it incessantly called another nearby. Gradually he noticed the fox’s wet breath was quickly freezing in the air after each call. It was late winter in Spitsbergen, Svalbard, and the air was -35C (-31F). Photographing Arctic foxes is often frustrating, as they are normally running around fast in search of food, but this one was very relaxed and let Marco get close enough to focus on it, with the light glowing perfectly in the background. (Photo by Marco Gaiotti/Wildlife Photographer of the Year 2021)

Wadha al-Sayyed, wife of captive Lebanese soldier Khaled Moqbel, protests for his release and government action, near burning tyres blocking a road in Beirut, December 15, 2014. More than two dozen members of the Lebanese security forces are being held by Sunni Islamists. (Photo by Hasan Shaaban/Reuters)

Women labourers work at the construction site of a road in Kolkata January 8, 2015. Across towns and cities in India, it is not uncommon to see women cleaning building sites, carrying bricks and or shoveling gravel – helping construct the infrastructure necessary for the country's economic and social development. They help build roads, railway tracks, airports, and offices. They lay pipes for clean water supplies, cables for telecommunications, and dig the drains for sewage systems. But although women make up at least 20 percent of India's 40 million construction workers, they are less recognized than male workers with lower pay and often prone to safety hazards and sexual harassment. They are often unaware of their rights or scared to complain, say activists now trying to campaign for better treatment of women in the construction industry. (Photo by Rupak De Chowdhuri/Reuters)

An Indian Sadhu, or Hindu holy man, sits for a community feast at the Sangam, the confluence of the Rivers Ganges, Yamuna and mythical Saraswati, during the annual month-long Magh Mela religious fair in Allahabad, India, Friday, January 16, 2015. Hundreds of thousands of devout Hindus are expected to take holy dips at the confluence during the astronomically auspicious period of over 45 days celebrated as Magh Mela. (Photo by Rajesh Kumar Singh/AP Photo)

Paramilitary policemen take part in a training in Chaohu, Anhui province, China December 28, 2015. (Photo by Reuters/China Daily)