Your Master Clock

Deep in your brain sits a cluster of about 20,000 neurons called the suprachiasmatic nucleus (SCN). It is your master clock.

Your master clock is not the only one. Your liver, gut, heart, and skin each run a local clock of their own, and the SCN keeps them in time like a conductor keeps an orchestra together. When that timing slips — through jet lag or a night shift — the whole body plays out of tune.