President Obama (from left), French President Francois Hollande and Microsoft co-founder Bill Gates applaud a speech during the Mission Innovation event at the UN conference on climate change Monday in Paris. Jim Watson/AFP/Getty Images hide caption

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Cellphones are everywhere in the developing world, as this Nairobi street scene shows. Bill and Melinda Gates believe the phones can be used for everything from farmer education to instant banking. Simon Maina/AFP/Getty Images hide caption

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By ensuring vaccines are invented and distributed, Bill Gates says, his foundation is dramatically reducing the number of childhood deaths in poor countries. Marie McGrory/NPR hide caption

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Satya Nadella, who's reportedly in line to be Microsoft's next CEO. Stephen Brashear/AP hide caption

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One experimental condom has tabs on either side so it's easier to put on in the dark. Courtesy of California Family Health Council hide caption

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Those are the hands of David Bradley, an original member of the IBM PC team and the inventor of the control-alt-delete function, hitting the right keys. Bob Jordan /AP hide caption

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There's no better deal than getting polio cases down to zero, philanthropist Bill Gates says. Marie McGrory/NPR hide caption

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This handshake between South Korean President Park Geun-hye and Microsoft founder Bill Gates sparked debate over whether the American — who kept his left hand in his pocket — had been rude. Other photos clearly show Gates' hand in his pocket.0 Lee Jin-man/AP hide caption

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