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 young exhibitor arrives with her kitten on a lead at the National Cat Club show at Crystal Palace, London. (Photo by Fox Photos/Getty Images). 2nd December 1931

Police walk past a burning car during riots in Birmingham City Centre on August 8, 2011 in Birmingham, England. After three nights of rioting and looting in and around London, the chaos is starting to spread to other cities around Britain. (Photo by Jeff J Mitchell/Getty Images)

Hamar women dance before a bull jumping ceremony in Ethiopia's southern Omo Valley region near Turmi on September 19, 2016. The Hamar are a Nilotic ethnic group in Ethiopia. The construction of the Gibe III dam, the third largest hydroelectric plant in Africa, and large areas of very “thirsty” cotton and sugar plantations and factories along the Omo river are impacting heavily on the lives of tribes living in the Omo Valley who depend on the river for their survival and way of life. (Photo by Carl De Souza/AFP Photo)

A seagull who turned bright orange after he plunged into a vat of chicken tikka masala in Beckford, England on June 9, 2016. The bird fell into a container of the food while trying to scavenge a piece of meat from a food factory bin in Wales. (Photo by Vale Wildlife Hospital/PA Wire)

Hawaii has long been known as a tropical paradise, but in recent years another image has intruded into the state's carefully crafted one of idyllic beaches and relaxing resorts: homelessness. The number of homeless people has grown in recent years, leaving the state with 487 homeless per 100,000 people, the nation's highest rate per capita, above New York and Nevada, according to federal statistics. Many of the homeless, however, defy the stereotype of the mentally ill or drug addicted. They are families, with men and women who work full-time jobs. They are struggling to get a foothold in a place with a high cost of living and low wages. Here: in this Thursday, August 27, 2015 photo, a homeless man drinks water while sitting on the beach at Ala Moana Beach Park located near Waikiki in Honolulu. (Photo by Jae C. Hong/AP Photo)

Yakelin Hernandez, 18, poses for a photograph near The Malecon where The Carnival was held, on August 14, 2015. Colorful costumes, dancing, parades and street parties on the Malecon in Havana, Cuba are all part of Havana Carnival 2015 which was held in August. (Photo by Sarah L. Voisin/The Washington Post)

Children try to walk through a flooded street at Kampung Melayu residential area in Jakarta, December 23, 2014. Torrential rains that have continued in Indonesia in recent days have widened the number of flooded areas that include Jakarta and Bandung, a local newspaper said on Tuesday. (Photo by Reuters/Beawiharta)