Cryo-electron tomography (cryo-ET), can be used to visualize and analyze cellular structures in their natural environment. Researchers at the MPI of Biochemistry in Martinsried and the University Medical Center Göttingen have now used cryo-ET to study protein folding helpers, so-called chaperonin complexes, in the bacterium E. coli. These chaperonins help newly synthesized proteins to fold into their correct, functional form. The researchers were able to illuminate the folding reaction with unprecedented detail, monitoring conformational changes in the chaperonin as well as its interactions with the client protein inside the folding chambers. The results have been published in Nature.