Donald Trump becomes the third US president in history to be impeached
The Democratic-led House voted in favour of two articles of impeachment - abuse of power and obstruction of Congress
He was accused of trying to extract political favours from Ukraine by withholding military aid
Addressing supporters at a rally in Michigan, Mr Trump said Democrats will be punished at the 2020 election
House Speaker Nancy Pelosi said it was "tragic" his "reckless actions" made this necessary. "He gave us no choice."
The next stage is a Senate trial in January, where he will probably be acquitted - as were predecessors Bill Clinton and Andrew Johnson
Developments have come thick and fast since a whistleblower came forward in the summer to raise concerns about a phone call President Trump made with Ukraine's president.
Here are some key moments from the inquiry, to bring you up to speed.
Trump could be impeached - how did we get here?
Image source, Getty ImagesJonathan Turley giving evidence to the impeachment inquiry
The articles for impeachment unveiled by House Democrats against President Donald Trump suggest this is a party putting haste before justice, says law professor Jonathan Turley, who appeared before the judiciary committee this month as a Republican witness.
"In my testimony before the House Judiciary Committee last week, I focused on the crimes like bribery that Speaker Nancy Pelosi and House Intelligence Committee Chairman Adam Schiff declared repeatedly were now well-established.
"Those claims were legally unfounded and untenable, though the other witnesses and members vociferously insisted that they were clear and established. The response was all too familiar. For three years, the same Democratic leadership told the public that a variety of criminal and impeachable acts were proven in the Mueller investigation. None of those crimes are now part of this impeachment.
"The Democrats have insisted on impeaching by Christmas rather than build a record to support such charges. They have burned three months without trying to compel witnesses like former national security adviser John Bolton.
"This is now the fastest investigation with the thinnest record supporting the narrowest impeachment in modern history. It is precisely what President Trump (who not surprisingly has supported the Democratic move for a fast impeachment) would relish. This schedule driven more by the Iowa caucuses in February than impeachment criteria."
It's begun.
The House has gavelled in. The Congressional chaplain gave a prayer and the pledge of allegiance was recited.
Members of the US House of Representatives have started debate and will soon decide the "rule" for impeachment, not impeachment itself. The rule is a procedural tool that determines how the today's debate will unfold - who will speak, and for how long.
Once this is done, they will move on to debate the articles of impeachment themselves.
There are a lot of people to keep tabs on in the impeachment saga. Here are a couple of the top Democrats and Republicans you'll see in the House of Representatives today.
Not quite sure what's going on?
Three BBC reporters based in North America, Ritu Prasad, Laura Trevelyan and Chris Buckler, break down the key points as the inquiry goes public.
Video by Shrai Popat
A beginner's guide to impeachment and Trump
BBC Newsnight's David Grossman has been to a swing district in Pennsylvania to meet a couple who were such hardcore Democrats that they named one of their ducks Obama (Joe Biden vanished, they say, possibly a victim of a coyote).
Now, Eileen and Richard Sorokas are huge fans of Donald Trump.
Their switch in allegiance reflects the voting patterns in Luzerne County where they live. It backed Barack Obama in 2008 and 2012, but turned to Trump in 2016.
So, what do they make of the impeachment charges Democrats have brought against the president?
"It doesn't sit very well with me at all," says Eileen who still considers herself a Democrat. "He hasn't done anything at all. It's all fabricated."
Richard says he voted for change, and a businessman who would shake up the Washington establishment.
"The only thing I dislike is all of his Tweeter remarks and smart Alec things, which isn't good for the country. But overall I believe he's doing a good job."
Pennsylvania is a key battleground state so how impeachment plays with voters here will impact the election result in November 2020.
Image source, Getty ImagesOnly months ago Democratic Speaker of the House Nancy Pelosi - one of the most powerful politicians in Washington - opposed impeachment, saying it was only worth doing if the process had some support from members of both political parties.
But now the House, which she oversees, is set to vote to impeach Trump strictly along party lines, without a single Republican expected to break ranks to oppose the president.
In March 2019, Pelosi told the Washington Post that she was “not for impeachment” because it would be “so divisive to the country that unless there’s something so compelling and overwhelming and bipartisan, I don’t think we should go down that path”.
Her comments came before reports that Trump sought to pressure his Ukrainian counterpart to open inquiries that would help him politically.
For Pelosi and other Democrats, the allegation that Trump endorsed - or even requested - foreign meddling in a US election - was the straw that broke the camel’s back.
“The facts of the Ukraine situation just changed everything,” she told reporters in early December.
"Say a PRAYER!" The president tweeted this morning while praising conservative news programme Fox & Friends and Republican congressman Doug Collins, who was on the show to defend Trump.
On Tuesday, Trump sent a scathing letter to Speaker of the House of Representatives Nancy Pelosi, criticising the impeachment inquiry.
Read our North America reporter's analysis on that letter here.
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Only two US presidents have been impeached before - Andrew Johnson and Bill Clinton. Richard Nixon was also investigated by Congress, but resigned before his almost certain impeachment.
Image source, GThe impeachment trial of President Andrew Johnson in 1868.
Image source, Getty ImagesA demonstration outside the White House in support of the impeachment of President Nixon in 1974
Image source, Getty ImagesThe House Judiciary Committee in 1974 recommends a third charge of willfully disobeying a Congressional subpoena against Nixon
Image source, Getty ImagesRichard Nixon announces his resignation from the White House, 9 August 1974
Image source, Getty ImagesPresident Bill Clinton pictured at an event in 1998 while the Republican-controlled House voted on his impeachment
Image source, Getty ImagesA protester outside the Capitol building during the impeachment trial of President Bill Clinton
Image source, Samuel Corum/Getty ImagesHistory possibly awaits. So how will the day play out?
Lawmakers will begin the day at 9am local (14:00 BST) with an hour of debate on the rules of impeachment.
Once that's decided, the House will move directly to six hours of debate, equally divided by party. If Republicans try to delay, this part could last up to eight hours.
Once debate is finished, lawmakers will vote on the articles separately. Abuse of power first, obstruction of Congress second.
If one or both of these pass, the House will appoint impeachment managers who will make the House's case in the upcoming Senate trial.
Students at Georgetown University Law Center in Washington DC have been taking a constitution law class, a few miles from the impeachment debate about to unfold in Congress.
So how much are they learning about this area of constitutional law?
Professor Susan Bloch took them through the key legal questions.
How US law professors teach impeachment
Lauren Turner
BBC News in Michigan
Image source, Getty ImagesSome Democratic politicians' constituents are angry.
Swing state congresswoman Elissa Slotkin knew she was in for a bumpy ride ahead of her appearance in front of hundreds of Michigan constituents on Monday morning.
The Democrat, who last year was elected to represent a district that voted for Trump, had announced just hours earlier that she was coming out in favour of impeachment.
She'd gone home to her farm in Holly at the weekend and sat at her desk with coffee and papers to weigh up the evidence in front of her. It was clear, the former CIA analyst decided, that the president's actions had crossed the threshold and that she was going to vote for the two articles of impeachment.
Now she had to stand up in front of 400 local residents to explain why.
Trump impeachment: Congresswoman booed in district
Image source, Getty ImagesTrump is accused of breaking the law by pressuring Ukraine's leader to dig up damaging information on a political rival.
In July, he urged Ukraine to investigate one of the Democratic frontrunners in next year's presidential election. This matters because it is illegal to ask foreign entities for help in winning a US election.
But there is a fierce debate about whether Trump broke the law or committed an impeachable offence - he himself says he has done nothing wrong.
Following weeks of hearings, the Democratic-led House of Representatives brought articles of impeachment against Trump, accusing him of abuse of power as well as obstructing Congress during the course of their inquiry.
Want more detail? Read the full story here.
Image source, Stephanie Keith/Getty ImagesNew Yorkers hold a rally on the eve of impeachment
US polls continue to find stark divides in the American public’s view of impeachment.
Polls released this week find that most Americans have not changed their minds since early October - remarkable given all that has happened since then.
Despite days of testimony from US officials who told lawmakers of the Trump administration’s efforts to pressure Ukraine for domestic political purposes, Americans are still almost exactly evenly split on whether to remove Trump from office.
According to a Fox News poll, 50% of Americans say Trump should be kicked out. An ABC/Washington Post poll found that 49% of Americans want him removed.
Both polls show that Republican support for Trump is rising.
The ABC/Wapo poll finds that 85% of Democrats say Trump should be impeached and removed, while 86% of Republicans say he should not be.
Seven out of 10 Americans believe Trump should allow his top aides to testify in the Senate trial.
One rare point of agreement? Six in 10 voters - from across the political spectrum - say they expect Trump to receive a fair trial in the Senate.
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Impeachment is the first part - the charges - of a two-stage political process by which Congress can remove a president from office.
If the House of Representatives votes to pass articles of impeachment, the Senate is forced to hold a trial.
A Senate vote requires a two-thirds majority to convict - unlikely in this case, given that Trump's party controls the chamber.
Only two US presidents in history - Bill Clinton and Andrew Johnson - have been impeached but neither was convicted and removed.
President Nixon resigned before he could have been impeached.
Need to catch up with all things Trump impeachment ahead of the vote? We’ve made it easy for you.
SIMPLE GUIDE: If you want a basic take on what's going on, this one's for you
GO DEEPER: Here's a 100, 300 and 800-word summary of the story
WHAT'S IMPEACHMENT? It's a political process to remove a president - video guide
THE VIEW FROM TRUMP COUNTRY: Hear from residents in West Virginia
A BUMPY RIDE: A newly elected Democrat sells impeachment to constituents
Welcome to our live coverage of the impeachment vote against President Donald Trump. It’s a historic day - the third-ever time this has happened in US history - as the House of Representatives, the lower-chamber of Congress, prepares to decide whether to formally accuse the president of two crimes and set the stage for a trial in the Senate.
The accusations levelled at the president? Abuse of power and obstruction of Congress.
We’ll keep you updated on all the latest happenings on Capitol Hill here.