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In January 2020 US President Donald Trump was impeached.

He was accused of abusing his power as president by pressurising Ukraine to dig up damaging information about Democrat Joe Biden - one of his main political competitors for this year's presidential election.

Only two other presidents in US history - Andrew Johnson and Bill Clinton - have ever been put on an impeachment trial.

Here's some facts you might not know about impeachment trials.

1. Presidents can be impeached more than once

The House of Representatives, who make laws and important decisions for America, can call an impeachment trial as many times as they want.

Although, so far in presidential history, once has been enough.

Back in 1974 Richard Nixon resigned as president before he could be impeached.

2. There's an electronics ban for this impeachment trial

There's no texting, no emailing - and even no talking allowed at President Trump's trial.

The Senate, where the trial is taking place, wants everyone to pay full attention, so any chatting or use of mobile phones is banned.

The rules also ban reading anything that's not directly related to the trial.

3. The impeachment trial may not call witnesses

Some experts predict witnesses might not be called during this trial if senators want to keep the trial short.

Trump himself may not even appear as a witness.

Out of the 100 senators, 53 of them are Republicans - Trump's party - and 47 of them are Democrats - the opposition.

That means if there is a vote during the trial to decide if witnesses will be heard from, the Democrats will need four Republicans to vote with them.

4. Senators might have to work at weekends during the trial

Senators are expecting to have to work over the weekend during the trial.

Usually they leave work before the end of the week, sometimes as early as Thursday, to do work in the areas where they are elected.

By working Saturdays, the Senate hope to speed the trial along more quickly, so it can be wrapped up sooner.

5. Impeachment costs a lot of money

The impeachment could tens of millions of dollars - but because we don't know how long it will last for, it's hard to estimate exactly how much that will be.

However, another recent US government investigation into whether Russia meddled in the last presidential election cost $32 million (£24.5 million) from start to finish.

The cost of the impeachment trial will be paid for by adults in the US through taxes.