Light helps you know when to sleep and when to be awake. When you open your eyes in the morning, sunlight lets your brain know it is time to wake up. As day turns to night, your brain makes a chemical called melatonin (mel-a-TONE-in) that makes you sleepy. Because light can wake you up, your room should be dark when you sleep. Even the light from a television or computer screen can make it harder to fall asleep. A dim nightlight is okay. You should have as much bright light in your room as possible in the morning to help "turn off" melatonin and wake you up!