Low-temperature electron micrograph of a cluster of E. coli bacteria, magnified 10,000 times; each individual bacterium is oblong shaped (image by Eric Erbe, digital colorization by Christopher Pooley, both of the United States Department of Agriculture, Agricultural Research Service, image ID K11077-1 (USA); retrieved via Wikimedia Commons; the image was modified by MIC). The cover is published under the Creative Commons Attribution (CC BY) license.