How do cats purr?

Now, there isn't really a special purring organ in a cat. It's simply a very fast movement of their voice box. So it's fast twitching of the muscles in their larynx which rapidly kind of flap up and down something called the glottis. That's some little flaps inside your throat, and it causes air vibrations when you inhale and exhale. And interestingly, a fact for you is that tigers, lions, jaguars, and leopards can only purr when they're breathing out!