Proteins control most of the body's functions, and their malfunction can have severe consequences, such as neurodegenerative diseases or cancer. Therefore, cells have mechanisms in place to control protein quality. In animal and human cells, chaperones of the Hsp70 class are at the heart of this control system, overseeing a wide array of biological processes. Yet, despite their crucial role, the precise molecular mechanism of Hsp70 chaperones has remained elusive for decades. Using a cutting-edge nanopore single-molecule technique, a team has now made a significant breakthrough in determining how Hsp70 chaperones generate the force needed to manipulate the structure of their client proteins.