Abstract
Mimivirus, the prototypic member of the new family of Mimiviridae, is the largest virus known to date. Progress has been made recently in determining the three-dimensional structure of the 0.75-microm diameter virion using cryo-electron microscopy and atomic force microscopy. These showed that the virus is composed of an outer layer of dense fibers surrounding an icosahedrally shaped capsid and an internal membrane sac enveloping the genomic material of the virus. Additionally, a unique starfish-like structure at one of the fivefold vertices, required by the virus for infecting its host, has been defined in more detail.