Governments across the world are investing large amounts of money in scientific research, often with the belief that such investments will increase economic growth--yet the scientific evidence for this belief is, as Colin Macilwain notes, "patchy." Science agencies are charged with identifying and funding the best science, yet there is little systematic information to guide their decisions: As the National Science and Technology Council's working group on Science of Science Policy has noted, the rationale for specific scientific investment decisions lacks a strong theoretical and empirical basis. There are important questions to be answered--and important contributions to be made by the policy research community. The Science of Science Policy Roadmap highlighted 10 overarching research questions; the papers in this JPAM issue provide an illustrative--but certainly not exhaustive--sense of the kinds of issues that can be addressed. The topic of prizes for innovation is a case in point. There has been an extensive policy debate about the potential role of using prizes to advance science and innovation versus the current dominant strategy of awarding grants through a scientific peer review process. Should funding agencies move to a different funding model? The Williams retrospective provides an overview of the literature in the field and identifies the lessons that might be useful for policymakers. Another vigorous debate--stimulated by changing federal policy on funding stem cell research--has been about the degree to which science investments could or should be conditioned by the political environment, and the potential consequences of changes in the level and volatility of such investments. Should politics and science mix? The Point/Counterpoint discussion between Owen-Smith et al. and Hurlbut and Robert both is thought provoking and provides a scientific basis for that debate. The summary provided in this article shows how the four papers in this special issue illustrate the way in which serious policy researchers can begin to answer important questions ranging from the impact of government action on energy production to the postdoctoral workforce, from pharmaceutical innovation to scientific innovation.