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

itoggle caption Marie McGrory/NPR

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

itoggle caption Lee Jin-man/AP

Bill Gates, co-founder of the the Bill & Melinda Gates Foundation, checks out a toilet demo at the Reinvent the Toilet Fair in Seattle, Wash. The festival featured prototypes of high-tech toilets developed by researchers around the world. Bill & Melinda Gates Foundation hide caption

itoggle caption Bill & Melinda Gates Foundation