“A Mothers Tail”. A baby cub pulls on his mother's tail to get attention. Photo location: Masai Mara, Kenya. (Photo and caption by Tori Marsh/National Geographic Photo Contest)

A picture shows the blood stained floor of a kindergarten following reported shelling in the rebel-held area of Harasta, on the northeastern outskirts of the capital Damascus, on November 6, 2016. At least four children were killed and 19 people injured in the government strike in Harasta, according to the Syrian Observatory for Human Rights. (Photo by Sameer Al-Doumy/AFP Photo)

Iraqi firefighters try to stop the fire of burning oil wells in Kirkuk, northern Iraq, 02 June 2016. Two Khabbaz oil field wells in Kirkuk Province, northern Iraq, exploded by suspected insurgents, a security official said. (Photo by EPA/Stringer)

Jorge (2nd R), 31, who is among members of lesbian, gay, bisexual and transgender (LGBT) community and his brother Paulo, 28, (R) laugh at Arouche Square in downtown Sao Paulo, Brazil, November 20, 2016. (Photo by Nacho Doce/Reuters)

An Indian cyclist pedals with a child during heavy rain in Mumbai, Maharashtra state, India, Friday, July 24, 2015. Several parts of the city witnessed heavy rain Friday. The monsoon rains which usually hit India from June to September are crucial for farmers whose crops feed hundreds of millions of people. (Photo by Rajanish Kakade/AP Photo)

Waura Indians wrestle during this year's “quarup”, a ritual held over several days to honour in death a person of great importance to them, in Xingu National Park, Mato Grosso State, Brazil August 25, 2013. (Photo by Ueslei Marcelino/Reuters)

Bra-clad Uber passenger was caught on camera stealing from a driver’s tip jar, while brazenly looking into the car’s security camera in New York City, USA in August (issued November 7, 2017). The unnamed rider was with two others. When they got out she looked around as she grabbed dollars out of the jar. The driver then looked down after the three got out, but it was too late. The publication later reported that the woman’s name is Gabita, and she’s 18 years old. (Photo by YouTube/The Epochtimes)

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)