TEHRAN, Iran -- It's been 40 years since Iranians came together to topple the shah.
Stirrings of opposition became apparent in 1975. The shah, Mohammed Reza Pahlavi, who had been reinstalled in 1953 after the CIA helped overthrow democratically elected Prime Minister Mohammad Mossadegh, used tough and sometimes brutal measures to clamp down on dissent.
He replaced Iran's two-party political system with a single political organization, downplayed the role of Islam in public life and used his internal security organization, SAVAK, to jail and sometimes torture opponents.
Street protests finally began in September 1978, when Iranians from all walks of life clashed with armed forces in Tehran, the capital.
Hundreds of lives were lost that day.
By late January 1979, after a series of bloody demonstrations, the shah fled to Egypt. And on Feb. 1, hard-line Islamist cleric Ayatollah Khomeini returned to Tehran from exile.
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While leftists joined forces with conservative Shiites to dismantle the monarchy, Khomeini's influence ultimately prevailed.
By June 1979, the secular, pro-American monarchy had been replaced with the Islamic Republic.
While several reformist and moderate politicians have been elected to govern Iran over the last four decades, in recent years, tough hard-line political and religious conservatives have become increasingly paranoid of Western influence and as a result have cracked down on people they perceive to be enemies of the state.
Here's a look at how Iran has and hasn't changed since Feb. 11, 1979, the date commemorated as the start of the revolution.