Nearly every cell has its own clock, coordinated by one master clock

Panda explains that circadian rhythms aren't confined to the brain's sleep-wake switch; nearly every organ — liver, pancreas, muscle, gut, even skin — contains its own molecular clock, built from oscillating genes that switch on and off in roughly 24-hour cycles, timing when that tissue is primed for activity versus repair.

These peripheral clocks are coordinated by a master clock, a cluster of neurons in the brain's hypothalamus called the suprachiasmatic nucleus, which takes its primary cue from light hitting the eyes and synchronizes the rest of the body's clocks to match. When the master clock and peripheral clocks fall out of sync with each other — as happens with jet lag, shift work, or erratic eating and light exposure — the body ends up running organs on conflicting schedules.

Panda's research suggests this internal misalignment, not just insufficient sleep, is a distinct and underappreciated health risk in its own right.

Takeaway: your liver, gut, and brain each have their own clock — health depends on keeping them all synchronized, not just on sleeping enough.