De Materia Medica (About Medicinal Materials) was written by Greek physician Dioscorides (ca. 40–90 C.E.) in the first century C.E. The manuscript included the names and uses of the 600 plants that, at the time, were known to have medicinal properties. The purpose of the publication was to improve medical service in the Roman Empire. In addition to its medical use, it became the book most often used for plant classification in the Western world for nearly 1,500 years. During the fifteenth and sixteenth centuries, European botanists and physicians used De Materia Medica to formulate their “herbals”—illustrated books on the medicinal uses of plants.