Coffee. Coffee beans with grinder. Coffee is a drink prepared from the roasted seeds of the coffee plant (Coffea sp.). The beans are ground in a grinder (upper left) to form a rough powder. It has been drunk around the Red Sea for over 1000 years. The drink contains caffeine, a stimulant chemical which increases heart rate and acts as a diuretic (increases urine production). The caffeine concentration is quite high in coffee, and several strong drinks in a short period may lead to caffeine intoxication. This manifests as insomnia, muscle twitches and rapid and rambling thought and speech.