This paper summarizes the latestresearch findings from a new body of empirical evidence thatuses randomized evaluations, similar to those used inmedical trials, to compare how one group responds to accessto specific new financial services against how a comparablegroup fares without those services. This paper goes back acouple of years to the first studies that used thisapproach, and summarizes a series of research studiespresented at the October 2010 microfinance impact andinnovation conference in New York. These studies evaluatedproduct design for a range of financial services, includingcredit, savings, and insurance. The studies discussed herewere undertaken by research affiliates of Innovations forPoverty Action (IPA), the Financial Access Initiative (FAI),and the Abdul Latif Jameel Poverty Action Lab (J-PAL) at theMassachusetts Institute of Technology; they are allrandomized evaluations unless otherwise specified. Part oneof this paper reviews the main results from randomizedevaluations that measure the impact of microcredit and microsavings on business investment and creation, consumption,and household well-being. Part two presents evidence fromevaluations of products and delivery design. Part threediscusses the evidence on micro insurance products.