Coffee is part of a group of stimulants that contain caffeine, one of the main chemicals in coffees, teas, chocolate, mate, sodas and caffeine pills. Caffeine is an alkaloid, belonging to the methylxanthine group, which includes theophylline and theobromine. In its pure form, caffeine is a white crystalline powder that tastes very bitter. All three chemicals are present in caffeinated drinks, and they work to stimulate the central nervous system, cardiac muscles, respiratory system and to delay fatigue. All these allow you to stay awake longer for those late-night cram sessions.
Caffeine is an addictive drug.
It operates using the same mechanisms that amphetamines, cocaine and heroin use to stimulate the brain. Yet, caffeine's effects are more mild than amphetamines, cocaine and heroin. Caffeine occurs naturally in many plants, including coffee beans, tea leaves and cocoa nuts. It is also found in a wide range of food products. Caffeine is added artificially to many others, including a variety of beverages.