Caffeine: Although caffeine is not a Natural Nootropic and considered a stimulant, it is known for providing the user a feeling of energy, concentration, and alertness.
L-Theanine is an amino acid found naturally in green tea. It enables the user to reach an optimal state of relaxed concentration without feeling drowsy. The brainwave patterns get altered into the same brainwave state experienced during meditation. When consumed as a supplement it is believed to reduce the symptoms of anxiety and neurodegeneration. L-Theanine increases the levels of dopamine, GABA, and neurotransmitters serotonin which improves mood, recall, learning, calm focus, and speed and accuracy of performance.
When caffeine and l-theanine are paired it suppresses the production of adenosine in our body and increases the production the f neurotransmitter dopamine. In other words, it seems that L-theanine negates the side effects of caffeine (jitteriness) while enhancing the positives (energy).