Two chemicals, serotonin and melatonin play an important role in regulating sleep.
Serotonin wakes you up, makes you feel energetic, alert and happy.
Melatonin makes you feel drowsy and ready to sleep.
Melatonin is actually converted from serotonin in response to exposure to light. When you’re exposed to bright light your brain makes serotonin; when the lights go dim, your brain converts the serotonin to melatonin.