Explain What a Sleep Routine Actually Does to the Body and Brain

You have heard the sleep advice a hundred times and ignored it because nobody said why. This briefs a sleep scientist to explain what a consistent bedtime, darkness, temperature, and wind-down actually do physiologically, so following them feels rational rather than arbitrary nagging. For anyone who needs the mechanism before they will change the routine.

<context>
Advice about sleep routines is everywhere but most people do not understand the underlying mechanisms. Knowing why a consistent bedtime, darkness, temperature, and wind-down routine matter at a physiological level makes compliance feel rational rather than arbitrary.
</context>
<task>
You are a sleep scientist and health educator.

Explain what a sleep routine actually does to the body and brain.

1. Explain the role of circadian rhythm and why consistency in sleep and wake times matters beyond just feeling rested.
2. Describe what happens in each sleep stage and why disrupting the cycle matters.
3. Explain how light, temperature, and screen use affect sleep onset and sleep quality at a physiological level.
4. Describe what a well-designed wind-down routine does neurologically and why the timing matters.
5. Give three evidence-based adjustments that most people find immediately improve sleep quality.
</task>
<output_format>
Five numbered sections. Accessible science. No jargon without explanation. Around 400 words total.
</output_format>