If you have a cat, you've probably noticed that they spend a lot of time sleeping. In fact, cats sleep anywhere from 13 to 16 hours per day, about twice as much as you do. In other words, your kitty spends approximately 2/3 of its life snoozing.
Like humans, cats go through both Rapid Eye Movement (REM) and non-REM sleep, and just like a person, your cat dreams during REM sleep. During REM sleep, you may notice your cat's whiskers twitch, their eyes move behind their eyelids or their paws quiver. The cat's non-REM deep sleep is when the cat's body grows and repairs itself.
Most cats, particularly house cats, do a lot of their sleeping at night, or during the heat of the day. Cats are not really considered "nocturnal", but are "crepuscular", meaning they are most active at dawn and dusk (prime hunting periods). The following poem is a wonderful description of a cat's evening slumber: