Two robotic legged squad support system (LS3) machines by the Defense Advanced Research Project Agency follow a technician during a demonstration at Joint Base Myer-Henderson Hall, Virginia, on September 10, 2012. (U.S. Marine Corps photo by Sgt. Mallory S. VanderSchans via The Atlantic)

(L-R) Ozzy Osbourne and son, producer Jack Osbourne visit the Tribeca Film Festival 2011 portrait studio on April 25, 2011 in New York City. (Photo by Larry Busacca/Getty Images for Tribeca Film Festival)

Model Bella Hadid celebrates her 20th birthday with her mother Yolanda Foster, The Weeknd and Shanina Shaik at Up & Down in New York City, NY on October 10, 2016. (Photo by TheStewartofNY/Splash News)

Playboy Bunnies pose for a selfie at the premiere of “The Transporter Refueled” at Playboy Mansion in Los Angeles, California August 25, 2015. The movie opens in the U.S. on September 4. (Photo by Mario Anzuoni/Reuters)

Miss Zero, whose real name is Sasha Frolova, of Russia celebrates winning the Alternative Miss World contest at Shakespeare's Globe theatre in London, October 18, 2014. The competition, which is open to entrants of any gender or nationality, was started by artist Andrew Logan in 1972. (Photo by Peter Nicholls/Reuters)

An Afghan girl harvests Cotton buds at a field on the outskirts of Balkh province, Afghanistan, November 15, 2014. (Photo by Sayed Mustafa/EPA)

It’s time to start watching for Comet PANSTARRS, one of two comets to get excited about in 2013. Photo: This image provided by NASA shoaws the comet PANSTARRS as seen from Mount Dale, Western Australia on March 5, 2013. According to NASA on March 10, it will make its closest approach to the sun about 28 million miles (45 million kilometers) away. As it continues its nightly trek across the sky, the comet may get lost in the sun's glare but should return and be visible to the naked eye by March 12. (Photo by AP Photo/NASA)

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)