The four hundred years which followed the explosive spread of Islam in the 7th century brough a unique fusion of cultures to Iran - unique because Iran embraced Islam while maintaining continuity with its own Persian heritage. The result was the great age of Iranian civilization, a broad culture created from the meeting of traditions: art and architecture flourished; Persian poetry flowered, in a language expanded by the rich Arabic vocabulary; great advances were made in science and medicine. Richard Frye describes these centuries as a high point in human achievement.