Here's what will happen next, and a look at the possible outcomes, after MPs voted down Theresa May's Brexit deal last night
No confidence vote - 7pm today
A vote of no confidence lets MPs vote on whether they want the Government to continue in office.
The motion must be worded: "That this House has no confidence in Her Majesty's Government."
This was tabled by Labour leader Jeremy Corbyn last night immediately following the Brexit deal vote.
If a majority of MPs vote for the motion then it starts a 14-day countdown.
If during that time the current government or any other alternative government cannot win a new vote of confidence, then an early general election would be called.
That election cannot happen for at least 25 working days.
However, it is likely the Government will win the vote. Tory MPs are unlikely to open the door to Labour.
And despite being unhappy with Theresa May's proposed Brexit deal, the Democratic Unionist Party (DUP) has indicated it will honour its "confidence and supply" deal with the Conservative Party.
The DUP would not wish to risk a Corbyn Government, as they have profound political differences with the Labour leader, particularly over Northern Ireland.
After the no confidence vote
Theresa May has said she will return to the House of Commons on Monday to give a statement on routes forward for Brexit.
If the Government survives the no confidence vote, it must move forward with Brexit plans.
It could look at a second vote on the same deal, or a similar one with tweaks in a hope to appease MPs who voted against it.
It also has a number of other options:
Renegotiation with the EU:
The Government could renegotiate a majorly amended deal with the EU which is more agreeable to Parliament. This would go beyond minor tweaks and reassurances.
This would likely take more time than is remaining before the withdrawal date of March 29, so the Government may seek an extension of Article 50 to delay Brexit.
This would require Parliament's approval, so a vote of MPs must take place.
The EU would also have to grant approval for the extension and re-negotiations, requiring all member states to agree.
If nothing else happens, the UK will leave the EU on March 29 without a deal.
The law is already in place, so this would happen automatically, an EU rules mean it must.
The Government may look to pass some laws to prepare for no deal, and could make smaller micro-deals with the EU on specific issues to minimise the impact of a no deal scenario.
A second referendum
This would also require an extension to Article 50 to allow time for the referendum to take place.
Even before Theresa May's deal was voted down, a number of MPs and campaign groups had been calling for a "people's vote" on the Brexit deal, or a second referendum on remaining in or leaving the EU.
There would need to me a new act passed by Parliament to approve the referendum taking place, the rules (including who could vote), the question and the date it takes place.
There would then need to be a specified "referendum period" before the vote takes place.
Experts have estimated the overall time needed to be 22 weeks - taking us way past March 29.
Calling a General Election
Even if the Government wins the no confidence vote, the Prime Minister may decide the only way forward is another General Election.
Theresa May could decide this is the only way to break the deadlock, by getting a political mandate from the public for her deal - and perhaps increasing her support in Parliament.
However, under the Fixed Term Parliaments Act 2011, UK general elections are only supposed to happen every five years. The next one is due in 2022.
So, again, calling a General Election would have to be voted through by MPs.
Two-thirds of all MPs would need to support the move. The earliest date for the election would be 25 working days later but it could be after that - the Prime Minister would choose the precise date.
But, again, this option could mean extending Article 50 is necessary.
Revoking Article 50
The European Court of Justice has already ruled the UK may unilaterally revoke Article 50 to cancel Brexit if it wishes - ie, without the approval of the other 27 EU countries.
However, this would also likely require approval by MPs - and the Government is still very committed to Brexit, making this option unlikely.
New Prime Minister
Theresa May has survived a vote of confidence from her own party, and another cannot be held for 12 months - which would take us to December.
She could decide to resign anyway if she cannot get her deal through and will not change course. Or she could come under intense pressure to resign from her MPs.
However, whoever took over from her would still have the same problems to overcome when it comes to getting a Brexit deal through Parliament.