Everyone knows that sleep is important factor for both mental and physical health. Proper sleep also enables you to be fully functional during the daytime. Sleep disorders (including difficulty falling asleep at night, poor sleep quality, early waking, circadian rhythm disorders) can be caused by many reasons i.e. stress, depression, anxiety, poor diet or an imbalance of chemical messengers and hormones in the brain namely serotonin and/or melatonin. The consequence of sleep disorders is often daytime fatigue. [1.]
What is melatonin?
Melatonin is your sleep hormone primarily produced by the pineal gland and released into the bloodstream exclusively at night by conversion from serotonin (5-ht) - your happy chemical messenger.  During your lifetime melatonin levels changes - In young children nocturnal melatonin levels are the highest and these decline gradually.  In older persons melatonin peak concentrations and total melatonin production could reduce. [4,5] The production of melatonin is triggered by photosensitive receptors at the back of the eye which send signals to the brain to convert serotonin in to melatonin.
What does melatonin do ?
Melatonin is important factor for the quality of your sleep and its management. Low levels of melatonin can cause you problems with falling asleep, disrupted sleep patterns or insomnia. There is significant evidence that links the hormone melatonin to your circadian cycle (the natural sleep and wake time) and supplementation with melatonin may improve both sleep duration and quality of those with an unusual daily schedule (jet lag, shift work, blind patients); or reduced concentration of melatonin levels (advancing age).  Melatonin synthesis is regulated by the blue light spectrum in both artificial and sunlight. [7,8] (hence why reading you phone in bed can prevent you from falling asleep). The process of creating melatonin in the pineal gland during darkness actually starts with an essential amino acid (a building block of protein) called L-tryptophan. L-tryptophan can do a lot of things, but one is that it can be converted in a four -step process via 5-htp, serotonin into melatonin. Sufficient tryptophan or 5-htp is critical to mood and the high-quality shut-eye we all need. 
What is 5-htp and where does it come from?
5-htp is a natural isolated nutrient extracted from the griffonia seed and it is the building block to your feel good chemical messenger serotonin (5-ht). Research has shown that 5-htp can be effective in increasing your body’s levels of serotonin , as well as being effective in treating insomnia and improving quality of sleep. [10-12] 5-htp naturally increases your serotonin levels during the day and melatonin at night. This process leads to improvement of your sleep cycle as it allows you to fall asleep faster, increases the duration of your sleep and enhance the overall sleep quality.
Take 1 tablet of 5-htp 90 minutes before bedtime.
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 GeoffroyPA, Etain B, Franchi JA, et al. Melatonin and melatonin agonists as adjunctive treatments in bipolar disorders. Curr Pharm Des.2015;21:3352–3358.10.2174/1381612821666150619093448
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 Zhao, Z.Y., Xie, Y., Fu, Y.R., Bogdan, A., and Touitou, Y. Aging and the circadian rhythm of melatonin: a cross-sectional study of Chinese subjects 30–110 yr of age. Chronobiol. Int. 2002; 19: 1171–1182
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 Jennifer E. Chase, Barry E. Gidal ; Melatonin: Therapeutic use in sleep disorders ; Volume: 31 issue: 10, page(s): 1218-1226 Issue published: October 1, 1997
Human melatonin regulation is not mediated by the three cone photopic visual system. Brainard GC, Hanifin JP, Rollag MD, Greeson J, Byrne B, Glickman G, Gerner E, Sanford B, J. Clin Endocrinol Metab. 2001 Jan; 86(1):433-6.
 Sensitivity of the human circadian system to short-wavelength (420-nm) light. Brainard GC, Sliney D, Hanifin JP, Glickman G, Byrne B, Greeson JM, Jasser S, Gerner E, Rollag MD, J. Biol Rhythms. 2008 Oct; 23(5):379-86.
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 Ryotaro Hara, Kuniki Kino; AMB Express. 2013; 3: 70. Published online 2013 Dec 9. doi: 10.1186/2191-0855-3-70