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)

Internationally acclaimed German three-dimensional artist Manfred Stader adds finishing touches to his artwork in Cape Town, South Africa on 21 November 2010. Stader created this masterpiece to celebrate the opening of Speedo's first dedicated concept store in Africa. (Photo by Foto24/Gallo Images/Getty Images)

Women perform a pole dancing routine during the national day celebration of “Urban Pole” dance along a street in Monterrey, Mexico, on June 9, 2013. (Photo by Daniel Becerril/Reuters)

The photographer holds up a Samsung Galaxy Tab 7.7 tablet at the Samsung hall at the IFA 2011 consumer electonics and appliances fair the day before the fair's official opening on September 1, 2011 in Berlin, Germany. The IFA 2011 will be open to the public from September 2-7. (Photo by Sean Gallup/Getty Images)

A design studio has launched its own dogs of war – by cleverly blending iconic Second World War planes with their canine counterparts. Photo: Wellington bomber with Golden Retreiver camoflage. A design studio has launched its own dogs of war – by cleverly blending iconic Second World War planes with their canine counterparts. (Photo by BNPS)

A child plays with a soap bubble on the city hall plaza on March 14, 2015 in Paris. (Photo by Dominique Faget/AFP Photo)

Students take part in a fashion and design entrance examination at Hubei Institute of fine Arts on February 28, 2011 in Wuhan, Hubei Province of China. 202 students took part in the exam and only 24, (10 percent) of them will be enrolled in Hubei Institute of fine Arts. (Photo by ChinaFotoPress/Getty Images). WUHAN, CHINA – FEBRUARY 28

Singer Shania Twain is honored with the 2442nd Star on the Hollywood Walk Of Fame on June 2, 2011 in Hollywood, California. (Photo by Jason Merritt/Getty Images)