Caffeine

The chemical structure for caffeine consists of two aromatic groups, two amide groups, and two amine groups.
Caffeine is a central nervous system stimulant of the methylxanthine class. It is the world's most widely consumed psychoactive drug.
Caffeine can produce a mild form of drug dependence--associated with withdrawal symptoms such as sleepiness, headache, and irritability--when an individual stops using caffeine after repeated daily intake. A person can also overdose on caffeine, which results in caffeine intoxication.
Caffeine reversibly blocks the action of adenosine on its receptor and consequently prevents the onset of drowsiness induced by adenosine.
Caffeine can cause sleep disruption or anxiety, as well as withdrawal symptoms such as sleepiness, headaches, and irritability.
In 1819, German chemist Friedlieb Ferdinand Runge isolated relatively pure caffeine for the first time and called it "Kaffebase." Popularity of caffeine beverages spread all over the world. Caffeine is still used today.
Caffeine is derived from the coffee bean, a misnomer for the seed of Coffea plants. Beverages containing caffeine are made by extracting caffeine via steeping the plant product in water.
Caffeine is FDA approved.

References:

Caffeine: Research