Eugene Danilkis, CEO of fintech startup Mambu, discusses banks' efforts to finance small and medium-size enterprises in developing countries, either indirectly (by funding microfinance organizations) or directly (by creating special lending subsidiaries unencumbered by legacy processes). He also explains how microfinance has moved beyond old stereotypes of lending to "basket weavers and fruit sellers"; why banks should heed Bill Gates' financial-inclusion message; and what the U.S. can learn from London about financial innovation.