Molecular chaperones are important biochemical proteins that mediate the correct assembly of polypeptide chains in building protein structure, but are not themselves components of the assembled structures. A common theme of chaperonin research is based on the study of their structural features and how they drive the folding of newly synthesized and denatured proteins. Almost all chaperonins, even the eukaryotic cylinder TRIC or CCT, are associated with specific cofactors that are involved in the folding process. A key aspect of Chaperonin Protocols is the purification of chaperonins from different species along with their corresponding cofactors, using examples that range from archeae to higher eukaryotes. The goal of this book is to give a representative overview, since there are many other species from which chaperonins might be purified. The protocols presented have all been successfully used by the contributors and are described in detail to be readily reproducible by structural biologists investigating the biochemical processes behind protein folding. There is a useful notes section which helps the user reflect the experience of the experimenter with the procedure, and is an effective tool for troubleshooting. Another main focus of the book is a group of chaperonin activity assays for in vivo and in vitro work, which can be applied to GroEL, mitochondrial Hsp60, as well as the eukaryotic chaperonin