Solar light bulbs

Denver (CNN) -- It started with such a simple concept: A solar light bulb that charges up during the day and lights the night when the sun sets.



Inventor Steve Katsaros perfected his design in June 2010, and four days later he had a patent in hand.

He knew it was a good product, but he didn't know what to do with it.

"It wasn't until after we created it that we asked ourselves, 'How do we market this,'" Katsaros says. "And we learned that the largest market was the developing world."

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