Early Bird or Night Owl? The Science of Your Body Clock

Some kids leap out of bed at 6 a.m. ready to go, while others could sleep until 10 if nobody woke them up. Scientists call this your chronotype, and it turns out it is wired into your brain, not just a habit you can flip on and off.

- What a chronotype is and why people have different ones - How the brain's suprachiasmatic nucleus (SCN) works as a body clock - What melatonin does and when your body releases it - How chronotypes shift as kids become teenagers

Deep inside your brain, in a region called the hypothalamus, sits a tiny cluster of cells called the suprachiasmatic nucleus, or SCN. It runs on a cycle close to 24 hours and resets itself using light that hits your eyes. When evening comes and light fades, the SCN signals a gland to release a hormone called melatonin, which makes you feel sleepy.

Researchers estimate roughly 25% of people are strong morning types, about 25% are strong evening types, and the remaining 50% fall somewhere in between. Genes play a real role - scientists have studied variations in a gene called PER3 that are linked to whether someone leans toward mornings or evenings. Age matters too: young children tend to be morning types, but during puberty, hormone changes push the body clock later, which is why so many teenagers naturally become night owls.

Because many teenagers' body clocks shift later, early school start times can force them to wake up before their brain is ready, creating a sleep debt that builds up over the week. Keeping a consistent sleep schedule, dimming lights before bed, and getting bright sunlight soon after waking all help reset the body clock and make it easier to fall asleep and wake up on time.