Yonta, 6, rests with her sister Montra, 3, and brother Leakhena, 4 months, under a mosquito bed net during monsoon season in July 2010, in Pailin province, Cambodia.
Paula Bronstein/Getty Images
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
Astrophysicist Szabolcs Marka has a radical idea: Use light as a barrier between mosquitoes and humans. He was awarded a $100,000 Grand Challenge grant by the Bill and Melinda Gates Foundation to see if the idea really works.
Courtesy of the Gates Foundation
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