Researchers have finally discovered the key to these fluff-ball's signature sound, which involves squishy pads in a cat's vocal cords.
Scientists have puzzled over how cats manage to make their distinctive low-pitched purr, as low frequency sounds are usually made by larger animals with longer vocal cords.
These 'purring pads' of connective tissue embedded in the vocal folds appear to increase the density, making them vibrate more slowly to produce the rumble that brings joy to their humans.
The international team led by voice scientist Christian Herbst from the University of Vienna in Austria says their research challenges the widely held belief that active muscle contractions are what cause purring.
Instead, the scientists think that purring may be a passive aerodynamic behavior that continues automatically after the brain sends an initiating signal.