Contrary to what many people think, Iran is not a stable Islamic state. The mullahs, like organized crime, have to hold their power over Iran with blood, the blood of their people. Yes, Iran, or Persia, as it was once called, has had their share of coups and revolutions, but for the most part, modern Iran's problems began in 1950 when foreign influence began to change the nature of the country. For many older people in the East, Western culture is as foreign to them as Eastern culture is to us.
The religious makeup of Iran before the 1979 revolution was mainly Shia Muslims, but a significant number of Jews, Christians, and other faiths called Iran home as well, and they all lived together just fine.