Leginon software is now available for download subject to the Apache open-source license at: www.leginon.org. The software for automated control and image acquisition from a transmission electron microscope (TEM) was developed by The Scripps Research Institute with funding from the National Center for Research Resources, National Institutes of Health, and has been marketed by FEI Co., of Hillsboro, Ore., since 2003. It is commonly used for single-particle analysis in which three-dimensional models of nanoscale particles are created. Leginon enables TEM users to collect very large numbers of high-quality images of macromolecules under low-dose conditions. The automated system is integrated with a database that keeps track of acquired images, the imaging parameters associated with them and the relationship among images acquired from the same target at various scales. Matt Harris, vice president of FEI’s NanoBiology division, said, "The widespread availability of this proven and highly functional software will accelerate scientific discovery and development in life sciences for many years to come.”