Egyptians will today vote in the second round of a referendum on disputed draft constitution that has polarised the country and plunged it into its worst crisis since the ouster of President Hosni Mubarak in last year's uprising.
The referendum and draft charter have pitted supporters of the Islamist Morsi against liberal parties, youth groups, Christians and a large group of moderate Muslims who fear the new document enshrines too big a role for Islam and undermines freedoms of expression, gender equality and rights of minorities.
The new crisis means the political instability that followed Mubarak's February 2011 overthrow will likely continue.
Here are some key events from 23 months of turmoil and transition:
January 25, 2011 - Egyptians hold nationwide demonstrations against the authoritarian rule of Mubarak, who has led the country for nearly three decades, protesting against police brutality and demanding social justice.
January 26 - A large security force moves into Cairo's Tahrir Square, beating and arresting protesters, using rubber bullets and tear gas. Three protesters are killed in similar protests outside of Cairo - among the first of what will become about 900 dead from clashes during the uprising.
January 28 - Protesters burn down the ruling party's headquarters and the military is deployed. Police virtually vanish from Egypt's streets, leading to a wave of looting, robbery and arson. Protesters occupy Tahrir square for a prolonged sit-in.
February 11 - Mubarak steps down and turns power over to the military. Two days later the body of top generals, the Supreme Council of the Armed Forces, dissolves parliament and suspends the constitution, meeting two key demands of protesters.
March 19 - Egyptians cast their first vote on constitutional amendments sponsored by the ruling military which set the timeline for the country's transition to democracy, including the first parliamentary and presidential elections.
November 28 - Voting begins in Egypt's first parliamentary elections since Mubarak's ouster. The election is held over a period of several weeks and concludes in January with nearly half the seats won by the previously banned Muslim Brotherhood.
April 20, 2012 - The presidential campaign officially begins. A first round of voting on May 23-24 determines that Morsi and Ahmed Shafiq, the last prime minister under Mubarak, will face each other in a runoff.
June 14 - The Supreme Constitutional Court rules to dissolve the Islamist-dominated lower house of parliament on grounds that a third of the chamber members were elected illegally. The military swiftly closes down parliament.
June 16-17 - Egyptians vote in the runoff between Morsi and Shafiq. The generals issue a "constitutional declaration" giving them sweeping authority to maintain their grip on power and limiting the powers of the president.
June 24 - Election officials declare Morsi the winner of Egypt's first free election, with 51.7 per cent of the vote.
June 29 - Morsi, now president-elect, delivers a rousing speech in Tahrir Square, vowing to fight on behalf of the people and to restore powers the generals have taken away from him.
June 30 - Morsi takes his formal oath before the Supreme Constitutional Court. A day earlier he had read a symbolic oath in Tahrir Square, the birthplace of the revolution.
July 8 - Morsi issues a surprise decree overruling the court's dissolution of parliament and challenging the generals.
July 9 - Parliament convenes in defiance of the court ruling disbanding it. In a short session it approves a new law that effectively places the panel tasked with writing the country's new constitution above judicial review.
August 12 - In a bold move, Morsi orders the retirement of the head of the ruling military council, longtime defense minister Field Marshal Hussein Tantawi and his chief of staff. He also cancels the military-declared constitutional amendments that gave the top generals wide powers and undermined his authority. The move was seen as way to curb the military's role in political affairs but it also gave Morsi the power to legislate in the absence of parliament.
November 19 - Several members of liberal parties and representatives of Egypt's churches announce their withdrawal from the 100-member constituent assembly tasked with writing Egypt's constitution, protesting what they said were attempts to impose ultraconservative Islamist content.
November 21 - Morsi negotiates a ceasefire deal between Hamas and Israel, after an eight-day conflict that threatened to widen into an Israeli ground operation into the Gaza Strip. It was a major diplomatic triumph for Morsi, establishing his role as a regional player with sway over the militant group Hamas, and influence with Israel and the US.
November 22 - In a surprise move, Morsi unilaterally decreed greater authorities for himself, giving the presidency, the panel writing the constitution and the upper house of parliament, both dominated by Islamists, immunity from judicial oversight. The move came just ahead of court decisions that could have dissolved the bodies.
November 23 - Days of protests follow Morsi's decrees, which were perceived as a power grab. Clashes between pro- and anti-Morsi supporters also erupted, and the offices of the Muslim Brotherhood were attacked in different governorates.
November 24 - Judges push back against Morsi's decrees, calling them an "unprecedented assault". Many courts begin an open-ended strike.
November 26 - Morsi meets with judges to tell them he does not intend to infringe on their authority. He does not back down from his decree, however.
November 27 - The opposition holds the largest rally to date against Islamists in Tahrir square. More than 200,000 people pack the square, chanting that Morsi should leave. Clashes between the president's supporters and opponents break out in other governorates.
November 30 - In a marathon session overnight, the Islamist-dominated panel writing the constitution rushes the draft through, seeking to preempt the court ruling that could dissolve the panel. The move renewed mass protests.
December 1 - Despite the protests, Morsi sets the referendum date for the disputed charter for December 15. Hundreds of Islamist protesters besiege the Supreme Constitutional Court, a day before it is set to rule on the legality of the panel that drafted the constitution.
December 2 - The Islamist protest outside the Supreme Constitutional Court leads it to cancel its ruling on the legality of the constitutional panel and declare an open-ended strike, calling it the "blackest day" in the history of Egypt's judiciary.
December 4 - More than 100,000 protesters march on the presidential palace, demanding the cancellation of the referendum on the constitution and the writing of a new one.
December 5 - Supporters of Morsi attack a sit-in outside the presidential palace in clashes that last through the night. At least 10 die in the fighting.
December 6 - Morsi refuses to call off the referendum, calling for a national dialogue in an address to the nation. The opposition rejects the call, saying it was not serious since Morsi refused to rescind any of his recent moves.
December 8 - Morsi cancels the decrees that gave him immunity from judicial oversight but keeps the referendum on time. Opposition vows to continue protests.
December 12 - Opposition calls on its supporters to vote no in the referendum. Pro- and anti-constitution demonstrations continue.
December 15 - Around a third of the 25 million voters eligible for the first leg of the constitutional referendum cast ballots, despite the judges' boycott. Unofficial results show that 56 per cent voted "yes" for the draft constitution.
December 16 - Egypt's rights groups say the constitutional referendum was marred by widespread violations.
December 18 - Prosecutor General Talaat Abdullah submits his resignation just a month after Morsi appointed him, following a sit-in by fellow prosecutors who accused him of pressuring a judge not to release some 130 anti-Morsi protesters from detention.
December 19 - Top elections official Zaghloul el-Balshi resigns, citing medical problem.
December 20 - Prosecutor General Talaat Abdaullah withdraws his resignation.
December 21 - Islamists hold massive rally in the country's second largest city of Alexandria to show solidarity with religious clerics.
December 22 - More than 25 million Egyptians eligible to vote will head to polling stations in 17 provinces to cast their ballots in the second round.