Chaperonins are a unique class of molecular chaperone that assist in the folding of newly synthesized, partially folded, and misfolded proteins. The importance of these folding machines is evident by their conservation across all three branches of life. The general structure of the chaperonins consists of 14-18 subunits, which form two back-to-back cavities. Unfolded polypeptide substrate is captured in one of the two cavities, and assisted to its native conformation in an ATP dependent fashion. The chaperonins can be separated into two, related, but unique groups. The group I chaperonins, typified by GroEL from bacteria, are fairly well understood, however, there are substantial gaps in our knowledge of the group II chaperonins, such as TRiC from the eukaryotic cytosol. Gaining a mechanistic understanding of the group II chaperonins is of great importance, as it has been shown that TRiC malfunction is associated with a variety of diseases. Toward this end the group II chaperonin conformation cycle, ATPase, and substrate folding mechanism have been investigated. This work elucidates key components of the folding cycle and greatly increases our understanding of these folding machines.