About the cover
Every research funding agency wants to support science that makes a difference, but there is no simple formula for identifying truly important research. And as funding gets squeezed, scientists face ever-stiffer competition for resources and jobs, and it becomes even more important to identify the best work. In a series of features and opinion pieces in this issue, we examine how the impact of research is measured — and ask whether todays evaluation systems promote the most influential science. Cover by Lorenzo Petrantoni.