Cover photograph (Copyright © 2003, American Society for Microbiology. All Rights Reserved.): Binding of hepatitis B virus surface antigen to Tupaia hepatocytes (with two nuclei each). After binding of subviral particles, surface antigen (red) was visualized with a monoclonal antibody and cells were counterstained with Meyer's hemalaun (blue). Magnification, X400. (See related article on page 9511.)