Donald Trump's impeachment trial will begin this week after he became the first US president last month to be impeached twice.
The US House of Representatives voted 232 to 197 to impeach him on January 13, just a week before he left office.
Now there will be a trial in the Senate to determine whether to convict him, a practice that could normally remove him from office.
Here's what you need to know.
Why was Donald Trump impeached for a second time?
Trump was impeached on a single article of impeachment for "incitation of an insurrection" over the events that occurred at the US Capitol on January 6.
Members of Congress say that he incited the violent mob that stormed the Capitol building by telling his supporters ahead of the attack to "fight like hell" and "to show strength" while repeating his baseless claims that the Democrats were attempting to steal the election as Congress was gathered to certify votes.
The former US president had maintained for weeks that the November election had been stolen from him and that he had in fact won by a landslide even though all of his challenges to the votes in key battleground states were thrown out in court.
Five people died and hundreds were injured as his supporters stormed the building on January 6, forcing the vice president and members of Congress to take cover.
"He threatened the integrity of the democratic system, interfered with the peaceful transition of power, and imperilled a coequal branch of Government," the article of impeachment reads.
The article of impeachment states that his actions are considered a "high crime and misdemeanour".
It took a mere week for the US House of Representatives to draft and vote on the article of impeachment, as many were witnesses to the events that occurred at the Capitol.
Is it likely that Trump will be convicted in the Senate?
It's not likely that Trump will be convicted in the Senate because it would require 67 Senators to vote in favour of conviction.
The 100-member Senate is currently split 50-50 between the two parties: the left-wing Democrats and right-wing Republicans.
Many Republicans have said they do not believe it is constitutional to try the former US president as he has already left office.
Republican Senator Rand Paul had argued that the procedure "would try a private citizen and not a president, a vice president or civil officer" and therefore violates the constitution. That led to 45 Republican Senators voting against holding an impeachment trial in a procedural vote.
The vote appeared to indicate that Democrats will likely fall short of the 17 Republican votes they would need to convict Trump.
Republican Senator Pat Toomey, who said he thinks the trial is constitutional, told CNN on Sunday that he thinks it's unlikely his colleagues would vote to convict.
He is one of five Republicans who voted with Democrats to determine that the impeachment trial was constitutional.
Trump's lawyers argued in a brief published by US media outlets on Monday that the Senate does not have jurisdiction over the former president because he is no longer in office, that the article violates his right to free speech and that the House rushed to issue the article of impeachment.
Trump has refused to testify at the Senate trial where the nine House impeachment managers, all members of Congress and lawyers, will present the case against him.
What would conviction mean for the former president?
Although the US Constitution gives the House of Representatives the "sole power" of impeachment, the Senate has the ability to hold an impeachment trial.
But a judgement or a conviction only extends "to removal from office" and "disqualification to hold enjoy any Office of honour, Trust or Profit under the United States".
Many Democrats argue that Trump should be held responsible for his actions in declaring the election fraudulent. They say that if he is convicted, he could be prevented from holding future office.
"If we convict him, we can then by only 51 votes remove him from ever running for office again," Senate Majority Leader Chuck Schumer told CBS News in an interview.
"I know we want to heal, but when something this awful happens, to just push it off will not heal."
Trump is only the third US president to be impeached and is the first president to be impeached twice, something that will likely have an impact on his legacy.
Trump was first impeached in December 2019 over withholding military aid to Ukraine in an effort to get officials to announce an investigation into his political opponent, now President Joe Biden.
There were two articles of impeachment against him: abuse of power and obstruction of Congress, but he was acquitted by the Senate in February 2020, mostly along party lines.