Melatonin is a sleep aid and is especially useful when you are traveling across time zones and suffer from jet lag. If you have any sleeping problems or insomnia, it is a good supplement to start with. Melatonin is a hormone normally secreted by your pineal gland to regulate your sleep cycle. Release of this hormone is stimulated by darkness and suppressed by light. If your melatonin secretion is low, this supplement will help return you to a normal sleep cycle. There can be many causes of insomnia and people with sleeping problems may need to try several different solutions to find one that helps the most. Melatonin is a good place to start.