Caffeine is an alkaloid; of which there are numerous compounds such as the methylxanthines, with three distinguished compounds: caffeine, theophylline, and theobromine, found in guarana, kola nuts, coffee, tea, cocoa beans, mate and other plants. These compounds have different biochemical effects, and are present in different ratios in the different plant sources. Caffeine is the most popular drug on the globe. It is a powerful stimulant to the Central Nervous System. Moderate use seems to be desirable by all, male and female; although excessive use can produce undesirable effects. Caffeine was discovered in 1820. In 1838, it was found that theine, a substance in tea, was identical to caffeine. Six or so caffeine containing plants are used more worldwide as a beverage than any other plants and herbal materials put together. The many caffeinated natural plants are coffee, tea, kola, cocoa, and guarana.