Boys pan for gold on a riverside at Iga Barriere, 25 km (15 miles) from Bunia, in the resource-rich Ituri region of eastern Congo February 16, 2009. Ituri is one of many areas of the country to have experienced bitter ethnic conflict between rival tribes in recent years. Massacres have left tens of thousands dead. It is this fighting that led U.S. authorities to take the unprecedented step of naming Congo in section 1502 of the Dodd-Frank financial regulation act, which says U.S.-listed companies that source gold, tungsten, tantalum and tin from Congo or its neighbours must assure the U.S. stock exchange regulator that their business is not helping fund conflict. (Photo by Finbarr O'Reilly/Reuters)

A young woman employee of North American Aviation Incorporated, working over the landing gear mechanism of a P-51 fighter plane, Inglewood, California, 1942. (Photo by Alfred T. Palmer/Buyenlarge/Getty Images)

(L-R) Singers Kelly Rowland, Beyonce and Michelle Williams perform during the Pepsi Super Bowl XLVII Halftime Show at the Mercedes-Benz Superdome on February 3, 2013 in New Orleans, Louisiana. (Photo by Ezra Shaw/Getty Images)

A baby bush-baby in a set of scales at London Zoo shortly after birth. (Photo by Fox Photos/Getty Images). 10th August 1938

A view of the screen of a ZaZZZ vending machine that contains cannabis flower, hemp-oil energy drinks, and other merchandise at Seattle Caregivers, a medical marijuana dispensary, in Seattle, Washington February 3, 2015. Vending machines selling medical marijuana opened for business in Seattle on Tuesday, in what the company providing them billed as a first-in-the-state innovation that it expects to expand to other cities and states where pot is legal as medicine. (Photo by David Ryder/Reuters)

A toddler sits on the winner of the giant pumpkin category during the RHS (Royal Horticultural Society) London Harvest Festival Show at RHS Lindley Halls on October 6, 2015 in London, England. The traditional harvest themed show runs October 6-7 and showcases a wide range of late summer grown fruit and vegetables. (Photo by Ben Pruchnie/Getty Images)

Electric cars sit charging in a parking garage at the University of California, Irvine January 26, 2015. “The Irvine Smart Grid Demonstration”, a $79 million project funded half by federal stimulus money and half by Edison and partners like UC Irvine, was launched in 2010. The $12 billion utility's research team Southern California Edison is testing everything from charging electronic vehicles via cell phone to devices that smooth out the power created by rooftop solar panels. Those are some of the roughly 60 projects in the works at Edison's Advanced Technology division. It has a small $19 million annual budget, but its influence far exceeds that. (Photo by Lucy Nicholson/Reuters)

An activist of the anti-G8 forum “Block G8” shows his middle finger to a police helicopter passing overhead June 07, 2007 at Bollhagen, near Heiligendamm, Germany. (Photo by Carsten Koall/Getty Images)