Pedanius Dioscorides (circa 40 - 90 AD) was a Greek physician, pharmacologist and botanist. He practiced in Rome at the time of Nero. He was a surgeon with the army of the emperor, so he had the opportunity to travel extensively, seeking medicinal substances (plants and minerals) from all over the Roman and Greek world. He is the author of De Materia Medica, an encyclopedia about herbal medicine and related medicinal substances that was widely read for more than 1,500 years. Unlike the case of many classical authors, his works were not rediscovered in the Renaissance, because his book never left circulation. De Materia Medica is the premiere historical source of information about the medicines used by the Greeks, Romans, and other cultures of antiquity.