Cellular proteins are produced as long chains of amino acids that must fold precisely into their final shape. The key players in this folding process are the so-called molecular chaperones, protein helpers that make sure this process is successful. Researchers from Utrecht University, in close collaboration with colleagues from Heidelberg University, have at last uncovered how the two most important chaperone families, Hsp70 and Hsp90, cooperate in this folding process. Surprisingly, it turns out they do not actively assist in the folding, as scientists had long assumed. Instead, they simply prepare the proteins for spontaneous, productive folding. This breakthrough in understanding the functioning of the Hsp70-Hsp90 cascade will be published in Molecular Cell on 3 May.