The chaperonin field has captured the attention of numerous scientists in recent years. A rapidly increasing number of reviews and articles have tried to elucidate the mechanisms by which these multimeric complexes drive the fo- ing of newly synthesized and denatured proteins. An obvious common theme of chaperonin research first arose from the study of their structural features. All members of this class consist of multiple subunits that form cylindrical structures, which encage proteins in a cave-like environment where folding of proteins takes place according to the current view. Since the chaperonin structures are found even in very primitive org- isms, the archaebacteriae, this "cave scheme" seems to be an evolutionarily successful feature that was conserved and that appears among evolutionarily distinct organisms. Interestingly, almost all chaperonins have specific cofactors that are - volved in the folding process. Even for the eukaryotic cylinder TRiC or CCT, a cofactor called prefoldin or GimC was recently discovered. Only for the archaeal chaperonins cofactors have not yet been discovered, although there seem to be GimC-like homologs in some archaeal species (unpublished obs- vations by M. Leroux).