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 worshipper throws vegetables into the crater as offerings during the Kasada Festival at Mount Bromo in Probolinggo, Indonesia's East Java province, August 1, 2015. Every year people gather for the annual festival where offerings of rice, fruit, vegetables, livestock or money are made to Hindu gods at the active volcano to ask for blessings and assure a bountiful harvest. (Photo by Reuters/Beawiharta)

UConn students from Storrs, Conn., Gary Tu, Danny Wang and Victor Zheng, fish at Shenipsit Lake in Tolland, Conn. during sunset on Tuesday, August 19, 2014. (Photo by Jim Michaud/AP Photo/Journal Inquirer)

“When I was 8 years old, my parents paid a smuggler to take me across the Himalayas, a weekslong walk over the mountains from Tibet to India. It was a trek that tens of thousands of other Tibetans have taken since the Dalai Lama fled a failed 1959 uprising against Chinese rule. My parents must have had their reasons to send me here; they must have had the best of intentions. But 18 years later, I still don't know why they did it. They are not political people. They are small farmers who raise barley and a few yak in a rural area not far from Lhasa, the Tibetan capital. I have not seen them since I left...”. – Tsering Topgyal via The Associated Press. (Photo by Tsering Topgyal/AP Photo)

A sculpture of Don Quixote shows him wearing the basin he mistook for the enchanted helmet of the fictional Moorish king Mambrino in Alcazar de San Juan, Spain, April 5, 2016. The arid central Spanish region of La Mancha is the setting for “Don Quixote”, the seventeenth-century novel by Miguel de Cervantes. Four hundred years after his death, references to the characters of Don Quixote, his loyal squire Sancho Panza and his beautiful lady Dulcinea abound in the surrounding villages from sweet treats to theatre productions involving livestock. Cervantes did not give away the name of the birthplace of Don Quixote, a middle-aged gentleman who becomes obsessed with chivalrous ideals. But many identify the village of Argamasilla de Alba as his hometown. The anniversary of Cervantes’ death is marked on the 23 April. (Photo by Susana Vera/Reuters)

Dancers perform during the carnival in Encarnacion, Paraguay on February 26, 2017. Encarnacion is located 375 km south of Asuncion, describes itself as the “Carnival Capital of Paraguay”. (Photo by Norberto Duarte/AFP Photo)

A student shouts slogans against Venezuelan President Nicola Maduro during a protest on the main highway in Caracas on March 30, 2017. Venezuela' s Supreme Court took over legislative powers Wednesday from the opposition- majority National Assembly, whose speaker accused leftist President Nicolas Maduro of staging a “coup”. (Photo by Juan Barreto/AFP Photo)

A performer wearing costumes walk on stilts before a show during a lantern fair at the beginning of Chinese Lunar New Year, in Xi'an, Shaanxi province, February 11, 2016. (Photo by Reuters/Stringer)