In 2010 Julia Silverman and Jessica Matthews traveled halfway around the world, hoping to light up some of the more impoverished villages of South Africa and Nigeria by testing some soccer balls there. But not just any soccer balls: Their Socckets, as they call them, house gyroscopic mechanisms that harness energy from the ball's motion. After being kicked around for 30 minutes, the balls can power a small LED lamp for three hours--long enough for a child whose home lacks electricity to do homework or read a book. Since most communities in Africa are crazy about soccer, the ball was a hit. "The kids thought it was magic," Silverman says, "but I could also see the wheels turning in their heads. One boy came back with a drawing of a ball with windmills sticking out of it. They wanted to be inventors, too."

The idea for the Soccket dates to an undergraduate engineering class at Harvard. There, Silverman and Matthews, working with two other students, drew on their experiences abroad--Matthews's family is from Nigeria, and Silverman had worked in sub-Saharan Africa--to devise a technically simple idea that could make a huge difference to the 1.4 billion people in the world living without electricity. The group knew that kerosene lamps emit dangerous fumes. While brainstorming alternatives, they thought of so-called shake flashlights, which are powered by motion, not batteries. Soon they'd put one inside a hamster ball to demonstrate how the global mania for soccer might help bring light to the places that don't have it. After the term ended, Matthews and Silverman worked with a design firm to create a more realistic prototype, a dead ringer for an actual soccer ball, except for the small plug on the outside.

In 2011 the duo quit their jobs at the World Bank (Silverman) and a social media start-up (Matthews) to focus on the Soccket. With sponsorship from corporations like Western Union, they've now produced more than 6,000 balls and accompanying LED lamps for distribution throughout countries including Mexico, El Salvador, and the Gambia. "We're also thinking of how everything from basketballs to volleyballs can be useful," Matthews says. "We want people to realize that making a difference doesn't have to be serious and boring. It can be as simple and fun as playing soccer."