How Does Caffeine Wake You Up?Caffeine is a bitter-tasting chemical related to the nucleic acid bases adenine and guanine.Produced by a range of plants to deter herbivorous animals from consuming their leaves or seeds, the compound is somewhat ironically prized by us humans for its flavor, not to mention its effect as a stimulant.In fact, caffeine is the most widely used psychoactive substance around the globe, with as many as four in five adults consuming the compound in the form of a hot or cold beverage such as coffee, tea, or soda, often to stave off drowsiness.