What does Iran's flag design mean?

The colors of green, white, and red are the traditional colors of Iran and of Islam which the country used under the previous government as well. There is also a red tulip in the center of the flag to represent the flowering of the Islamic Republic. In small white letters both above and bellow the white band it says "Allah hu Akbar" which means "God is the Greatest" and is another symbol of Iran's Islamic nature.