Nitric oxide is a gas that's found outside and inside your body. In the environment, nitric oxide can be toxic at high levels. But at the low levels inside your body it acts as a chemical messenger, ...

Melatonin is a hormone made by the pineal gland, which is located in the middle of your brain. Melatonin encourages good, healthy sleep. Your melatonin levels naturally go up at night, a few hours ...