What’s the best way to spend $100 million to fix one huge problem in the world today? That is the challenge laid down by the MacArthur Foundation in Chicago, distributors of the “genius grant”. Ed Butler and a panel of expert guests hear the details of four of the final eight challengers, with ideas to transform the quality of the food we eat and to train eye surgeons to restore sight to vast numbers in Nepal, Ethiopia and Ghana. Is $100 million enough to tackle these challenges and what are the consequences, intended or not, of philanthropy on such a big scale?