Why do I feel sleepy at bedtime?

1. 1

   Fuzz says

   Deep inside your brain is a tiny clock that keeps track of the day, all twenty-four hours of it. When evening comes, your brain clock starts telling your body it's time to wind down. That's why you feel cosy and sleepy at bedtime.

   For ages 4–7
   Hear Fuzz

   Checked against Circadian rhythms (NIGMS, US National Institutes of Health)

2. 2

   How does my brain clock know it's evening?

   Your eyes keep telling your brain clock how much light there is. As the light fades in the evening, the clock tells your brain to make more of a sleepy helper called melatonin. Melatonin gives you that drowsy feeling that makes your bed feel so good.

   For ages 6–9
   Hear Fuzz

   Checked against Circadian rhythms (NIGMS, US National Institutes of Health)

In Lil' Phil, reaching the bottom of this wonder earns a sticker for Fuzz's collection.

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  Ages 4–11Fuzz
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