As early as the Stone Age, humans began to use caffeine. Early people found that chewing the seeds, bark or leaves of specific plants can relieve fatigue and refresh the mind. It was not until many years later that people discovered that soaking these plants in hot water could increase the efficacy of caffeine. Many cultures have myths about people discovering these plants in ancient times.

According to an ancient Mongolian myth, Shennong, the emperor of China around 3000 BC, accidentally discovered that when some leaves floated into boiling water, they would produce a fragrant and refreshing drink. An ancient book about tea, Lu Yu's Tea Classic, also mentioned Shennong's name.