Cover photograph (Copyright © 2000, American Society for Microbiology. All rights reserved.): Nidogen 1, a ubiquitous component of basement membranes, has been considered to play a key role in their stabilization. Surprisingly, mutant mice lacking nidogen 1 develop normally, showing no ultrastructural changes in the basement membranes. In most organs (such as the kidney, which is shown here), nidogen 2 immunostaining is found in all basement membranes without alterations upon the loss of nidogen 1. However, in some tissues, such as skeletal muscle and the heart, there is striking evidence for a redistribution of nidogen 2 in the absence of nidogen 1. These results demonstrate that nidogen 1 is not required for basement membrane formation or maintenance. (See related article on page 7007.)