join me next time for a conversationings with benedict cumberbach, star of the film "the imitation game time. we'll see you then. and by contributions to your pbsh/ station from viewers like you. thank you. >> pbs. be more. pbs. >> be more. pbs. >> rose: welcome to the program. tonight bill and melinda gates. >> when you let your heart break and think of what it would be like to deal with a child dying of malaria. you say to yourself my gosh, we have to save not just that childe-rqnc0@6cexjbut 600,000 children. and that can be done. if you let your heart break but then you come home and you take all the science meeting and you see all the great innovations and you figure out how do i deliver those things in these difficult remote settings in africa. i think that sets up learning for the foundation over the last 15 years. not just how to do the great science but also how to deliver it in these remote settings. >> philanthropy is more about pilot programs, innovation. some of the research things that it's so risky it wouldn't get done otherwise. as a percentage of the dollar, the overall