Experienced researchers present readily reproducible protocols for studying the intracellular proteins that are critical to many biological processes. They include methods for purifying chaperonin from different species and their corresponding cofactors, activity assays for and work, assays for GroEL that can also be applied to mitochondrial Hsp60, assays for the eukaryotic chaperonin TRiC, and methods such as preparing labeled probes that can be used for various purposes and procedures.