Caffeine is found as theine in tea. It is also a xanthine alkaloid found in the leaves and beans of the coffee tree, yerba mate, guarana berries, and also in small quantities in cocoa, the kola nut and the Yaupon holly.
In plants, caffeine acts as a natural pesticide that paralyzes and kills many insects feeding upon them.
Caffeine is a central nervous system (CNS) stimulant, having the effect of warding off drowsiness and restoring alertness.
Caffeine-containing beverages, such as coffee and tea, have got great popularity, making caffeine the world's most popular psychoactive substance.