Theophrastus and Dioscorides were two early writers on herbalism. Theophrastus, a student of Aristotle and Plato, wrote one of the earliest classifications of plants. Dioscorides, a Greek physician, wrote De Materia Medica between 50-70 AD which described around 600 plant species and their medical uses. Herbal medicine, also called botanical or phytomedicine, refers to using plants for medicinal purposes and has a long tradition outside conventional medicine. Herbalism can treat many conditions and its main benefit is boosting energy and strengthening internal organ functions.