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)

Porcelain Black performs during the ' I Am Still Music' Tour at the Wells Fargo Center on March 26, 2011 in Philadelphia, Pennsylvania

Activists protest the Shell Oil Company's drilling rig Polar Pioneer which is parked at Terminal 5 at the Port of Seattle, Washington May 16, 2015. Hundreds of activists in kayaks and small boats fanned out on a Seattle bay on Saturday to protest plans by Royal Dutch Shell to resume oil exploration in the Arctic and keep two of its drilling rigs stored in the city's port. (Photo by Jason Redmond/Reuters)

Vitaly Gorshkov, a wildlife photographer, captured these animals in their natural habitat. He says that these animals are so hairy that it is difficult to distinguish the front from the back. The oxen aren’t really afraid of humans that is why it is easy to approach them and take pictures.

This close-up image – of a Holi Festival celebrant in Vrindivan, India, coated in neon-colored powder – was submitted to National Geographic’s Your Shot in the last week of March. On April 1 we published it on our Daily News site, along with seven other bright scenes captured during the Hindu spring Festival of Colors. (Photo by Tinto Alencherry/National Geographic)

A wild monkey has stunned animal lovers after it adopted an abandoned kitten and cared for it as his own. The young long-tailed macaque monkey was spotted in a forest protectively nuzzling and grooming the ginger kitten, making sure no harm came to it.

Ucil, a trained monkey, takes part in a street performance on June 1, 2011 in Jakarta, Indonesia. The street performances usually involve the monkeys wearing masks, such as dolls' heads or attire to mimic humans, with the monkeys trained to act out human activities such as shopping, riding bicycles or other simulations of human behaviour. Poverty drives the handlers to exploit the monkeys in the hope of earning small change, but the effect and cruelty to the monkeys is a cause that charities such as the Jakarta Animal Aid Network are increasingly taking up. (Photo by Ulet Ifansasti/Getty Images)

“Cassowaries are large, flightless birds related to emus and (more distantly) to ostriches, rheas, and kiwis”, writes Olivia Judson in the September issue of National Geographic magazine. How large? People-size: Adult males stand well over five foot five and top 110 pounds. Females are even taller, and can weigh more than 160 pounds. Dangerous when roused, they’re shy and peaceable when left alone. But even birds this big and tough are prey to habitat loss. The dense New Guinea and Australia rain forests where they live have dwindled. Today cassowaries might number 1,500 to 2,000. And because they help shape those same forests – by moving seeds from one place to another – “if they vanish”, Judson writes, “the structure of the forest would gradually change” too. (Photo by Christian Ziegler/National Geographic)