L-theanine is a chemical that exists in the leaves of green tea plants, it gets extracted and put into pills or other forms. Its main purpose seems to be relaxation, making you calm down and relax.
It is found in green tea, which means that it probably originates from something to do with plants.
It has the ability to cross the blood–brain barrier, unlike caffeine or any of its analogs.
It’s nootropic effects have been widely studied and documented.
In some cases, it has been found to be as effective as anti-depressants for mild depression.
It has also been shown to increase alpha wave production in the brain, which is associated with a state of relaxed wakefulness.