Media captionHow did we get here?
The US House of Representatives has impeached President Donald Trump, and the Republican leader now faces a trial in the Senate.
Members of the upper house will decide whether to remove Mr Trump from office. As the Republican party hold a Senate majority, he will likely be acquitted.
But House impeachment managers – in essence, the prosecutors – will try to convince senators that the president should be ousted from the White House, for abuse of power and obstruction of Congress.
It is the third time an impeachment trial has happened in the Senate.
Here is our guide to the cast of characters, including the lawyers who will defend Mr Trump and those who will seek to have him removed from office.
Senate Majority Leader Mitch McConnell
This is not the first impeachment for some of the key players in this political drama. Mr McConnell took part in impeachment and Senate trial of President Bill Clinton in 1999.
Image copyrightEPA and ReutersImage caption
Mitch McConnell (left) is setting out the rules of the trial with Senate minority leader Chuck Schumer
Back then, he was the chair of the Senate Rules Committee, and a member of the “Conservative Coalition” – a bi-partisan group of senators representing southern states.
Mr McConnell is currently setting out the rules of the trial with the minority leader, Democratic member Chuck Schumer – although as majority leader, Mr McConnell will have the final say.
The Republican senator drew fire after he said there would be “total co-ordination” with the White House in the process. Senators are expected to act as impartial jurors in the process.
Currently, he is battling with Democratic leaders over whether or not witnesses and documents will be allowed in the trial.
Chief Justice John Roberts
Mr Roberts is the youngest chief justice of the US in more than 200 years, taking the position in 2005 at the age of 50.
He made his older colleagues laugh recently when he referenced the phrase “OK Boomer” in a Supreme Court session.
Mr Roberts will preside over the impeachment trial, making sure all sides stick to the rules. He swore in senators as jurors early in January.
Image copyrightEPAImage caption
John Roberts is the youngest US chief justice in more than 200 years
He is ideologically conservative, although he has worked with liberal judges on the Supreme Court before and has repeatedly stated his belief that the body should be non-political.
Mr Roberts rebuked Mr Trump two years ago when the president criticised a jurist who did not back his immigration policies as an “Obama judge”.
“We do not have Obama judges or Trump judges, Bush judges or Clinton judges,” Mr Robert said.
“What we have is an extraordinary group of dedicated judges doing their level best to do equal right to those appearing before them.”
Congressman Adam Schiff, Democrat
Mr Schiff is the leader of the seven House impeachment managers: he and Jerry Nadler, as well as House of Representatives members Jason Crow, Val Demings, Hakeem Jeffries, Zoe Lofgren and Sylvia Garcia.
Image copyrightAFP/GettyImage caption
Adam Schiff, right, will lead the team with the help of Jerry Nadler, left
These Democrats will lay out the case against the president in a bid to have him removed from office.
Mr Schiff represents California’s 28th congressional district and is chairman of the House Intelligence Committee.
As such, he has become the face of the impeachment proceedings, and a hate figure for Mr Trump and his supporters. The president has launched furious attacks against the Massachusetts-born 59-year-old.
Mr Schiff said he was “humbled” by his appointment as lead prosecutor. Admirers see him as the man with extensive knowledge of the impeachment case, best suited to present it to the Senate.
Congressman Jerry Nadler, Democrat
Another key figure in the Democratic impeachment process is Mr Nadler, the head of the House Judiciary Committee.
A New Yorker, the 72-year-old has served as a congressman since 1992, and has a reputation as a passionate defender of civil liberties with a very liberal voting record.
Media captionDemocrat Jerry Nadler announces the articles of impeachment
Like Mr McConnell, he was also in politics during the last impeachment. The Congressional record shows he referred to President Clinton’s impeachment as a “partisan railroad job” in 1998.
White House counsel Pat Cipollone
Mr Cipollone will lead Mr Trump’s defence, alongside the president’s personal lawyer Jay Sekulow.
Image copyrightReutersImage caption
Pat Cipollone has served as White House counsel since December 2018
Before now, his biggest role in the impeachment proceedings were letters he sent to Mr Nadler, declaring that the White House would not take part in the inquiry and describing the process as a “charade”.
Mr Trump named Mr Cipollone as White House counsel in December 2018.
He also advised the president during Special Counsel Robert Mueller’s investigation into Russian interference in the 2016 election.
Jay Sekulow, personal lawyer to the president
The New York lawyer is the chief counsel at the American Center for Law & Justice, a conservative organisation. He is known to have deep ties to the evangelical community.
Image copyrightGetty ImagesImage caption
Mr Sekulow is also in the Jay Sekulow Band, a rock group which features former Kansas member John Elefante
He has argued in front of the US Supreme Court a number of times – including staunch defences of religious freedoms.
For the president, Mr Sekulow served as a key figure in Mr Trump’s legal team during the Mueller inquiry.
Image copyrightReuters and Getty ImagesImage caption
Ken Starr, Pam Bondi and Alan Dershowitz have joined the president’s defence team
Mr Starr is best known for his work as the independent counsel for the Whitewater controversy, an investigation into real estate investments by Bill and Hillary Clinton.
This eventually widened into an investigation into President Clinton’s affair with White House intern Monica Lewinsky. The Starr Report, published in 1998, led to Mr Clinton’s impeachment.
He was succeeded as independent counsel in 2002 by Robert Ray – another member of Mr Trump’s Senate trial defence team.
Media captionTrump and Clinton’s impeachment – what’s different?
A Republican originally from Texas, Mr Starr has argued 36 cases before the Supreme Court.
The retired Harvard University professor is an expert on US constitutional law.
Mr Dershowitz has served on a number of famous cases. He defended OJ Simpson as a member of the so-called “Dream Team” during the American football star’s murder trial, and has represented celebrities like Mike Tyson and Patty Hearst.
Image copyrightGetty ImagesImage caption
Alan Dershowitz defended OJ Simpson in 1995
Speaking to CBS News, the lawyer said he was “very, very concerned” about the precedent this impeachment could establish, and said he agreed to serve Mr Trump “as an independent constitutional scholar”.
“I take no position on the politics – just on the constitution.”
Other members of the team include Pam Bondi, former Florida Attorney General, and lawyers Eric Hershmann and Jane Raskin.
Senators are supposed to be impartial jurors during the impeachment trial. But the expectation is that this will be a highly partisan vote.
The Senate needs a two-thirds majority to remove Mr Trump from power. Given that Republicans hold 53 seats in the upper house, it is likely the president will be acquitted.
But Mr Trump has critics within his own party. Republican Senator Lisa Murkowski said she was “disturbed” by her party’s stance in the wake of Mr McConnell’s comments about “total co-operation”, given the need for impartiality during the trial.
Image copyrightReuters and EPAImage caption
Lisa Murkoswki, left, is a senator for Alaska while Mitt Romney is a senator for Utah
US media suggest that former presidential candidate Mitt Romney, as well as Ben Sasse and Susan Collins, are also important Republican senators to watch as the trial continues to see exactly how they react to the evidence.
However, media outlets also say two Democratic senators – Doug Jones and Joe Manchin – could even be persuaded to side with the Republicans and vote no, under pressure from their constituents.
While it is likely a foregone conclusion, these are the senators to watch.
Want to find out more on impeachment?
Media captionHow did we get here?