(I) Caffeine occurs in several plants including the familiar coffee bean, the tea leaf and the cocoa bean. (II) Most human societies use caffeine regularly, most often in beverages, for its stimulant effect and flavor. (III) Caffeine contents of beverages vary depending on the plants they are made from, the grind or cut size and the method and the duration of brewing. (IV) In developed countries drug industries use caffeine in many kinds of drugs. (V) In general a cup of coffee contains the most caffeine, a cup of tea less than half much, and cocoa less still.