THE BILL AND MELINDA GATES Foundation made headlines this summer when they pledged $41.5 million to reinvent the toilet—a life-saving sanitation device that remains out of reach for many in developing nations. But another program, Grand Challenges Explorations—accepting applications this month—is set to provide equally crucial theme-based grants. Previous topics range from next-gen sanitation to malaria eradication to utilizing cellphones to increase awareness of the need for childhood vaccinations. Recent funding, says spokesperson Katie Harris, went toward engineering bacteria that will eradicate a pathogen responsible for diarrhea and traps that help prevent the spread of malaria by luring mosquitoes with the synthetically replicated stench of human feet.