Your kitty's purring is not just for show.
All feline lovers know that cats purr when they're happy, but cats also purr to self-soothe when frightened or stressed, and possibly to self-heal when they are injured or in pain. Researchers speculate that the vibrations stimulate muscles and bones without expending a lot of energy. And in tests, the frequency of cat purrs matched the frequency known to improve bone density and promote muscle healing.