Cover photograph (Copyright © 2008, American Society for Microbiology. All Rights Reserved.): Structure without crystal. The picture at upper left shows a three-dimensional reconstruction of the canine adenovirus at 12-Å resolution as determined by cryoelectron microscopy. The pentons are colored in blue-green. A computer model of canine adenovirus type 2 fiber is shown at the bottom. An icosahedral quartz crystal which diffracts light is also shown. (See related article on p. 3192.)