Follicular cells contain built-in circadian clocks that literally track your sleep cycles, meaning your individual strands of hair possess cellular knowledge of exactly when you go to bed.

A closer look

Follicular cells contain built-in circadian clocks that literally track your sleep cycles, meaning your individual strands of hair possess cellular knowledge of exactly when you go to bed. Scientists can extract RNA from your hair follicles to accurately determine if you are an early bird or a chronic night owl without ever asking you a single question. Your body is basically operating an integrated microscopic surveillance state, recording your terrible sleep hygiene directly into the physical structure of your scalp. You can lie to your doctor about getting eight hours of rest, but the split ends on your head are ready to testify in court about those late-night doom-scrolling sessions. It is slightly unnerving to realize that every single time you brush your hair, you are styling thousands of tiny biological informants that know all your secrets!