The talks on the terms of Britain's withdrawal from the European Union are finally getting under way in Brussels.
Here are the key questions surrounding the Brexit negotiations.
:: Who is sitting round the table?
The UK side is led by Brexit Secretary David Davis, the committed Leaver who is spearheading the British negotiating effort. On the opposite side is Michel Barnier, the French former foreign minister who is the European Commission's chief negotiator. They will each be accompanied by a team of senior officials.
:: What will they be discussing?
Both sides agree a top priority is sorting out the rights of the 3.2 million EU nationals living in the UK and the 1.2 million British expats in the EU. Both say they want a reciprocal agreement although the Europeans say the British side does not appear to appreciate just what that involves.
:: What else?
Other issues that have to be sorted include the status of the border between Northern Ireland and the Irish Republic.
And then there is the "divorce bill". The EU side has been suggesting it will be looking for a settlement of around £50 billion in respect of the UK's outstanding liabilities. British ministers insist the final sum will not be anything like that. Expect plenty of wrangling to come.
:: Is Britain also looking for a free trade deal?
It certainly is. Mr Davis has said that while the UK is pulling out of the single market and the customs union and ending the free movement of labour, he wants an agreement that replicates as far as possible Britain's existing trade arrangements with the EU.
:: Will he get it?
Europe's key power brokers like Germany's Angela Merkel and France's Emmanuel Macron are adamant Britain cannot expect to enjoy all the benefits of EU membership from outside the bloc. Mr Barnier has said talks on a trade deal cannot even start until sufficient progress has been made on the other issues. It could be a bumpy ride ahead.
:: How often will the two sides be meeting?
It is expected talks will take place once a month in Brussels as they work through the issues to be resolved.
:: How long have they got to sort this out?
Britain is due to leave the EU at midnight Brussels time (11pm in the UK) on March 29 2019 - unless an extension is agreed by all 27 remaining member states. - with or without an agreement. In practice that is likely to mean the negotiations will need to be wrapped up by the autumn of 2018 in order to allow time for the deal to be ratified.
:: What will ratification involve?
The European Court of Justice is expected to rule on whether a deal must be approved by the parliaments of the individual member states, Theresa May has promised MPs at Westminster a vote, and finally there will be a vote of the European Parliament. It could be quite a tall order.