Everyone knows that caffeine can keep you awake, but a new study shows that the world's most popular drug can actually interfere with your body's internal sense of time.
"The circadian clock is way beyond 'sleep and wake,' " says Kenneth Wright, a sleep and circadian physiologist at the University of Colorado, Boulder. "The circadian clock is present in cells throughout our entire body. It's in your fat cells; it's in your muscle cells. It's in your liver, for example, as well as in your brain."