What's the scope of the special counsel investigation?

Robert Mueller is authorized to investigate "any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump."

Mueller's remit also allows him to potentially broaden the scope of the probe and look into "any matters that arose or may arise directly from the investigation."

Mueller's jurisdiction as special counsel also authorizes him to "investigate and prosecute federal crimes committed in the course of, and with intent to interfere with, the special counsel's investigation, such as perjury, obstruction of justice, destruction of evidence, and intimidation of witnesses."

What powers does a special counsel have?

Essentially, a special counsel has the same powers as a regular federal prosecutor, with the difference being that he or she operates outside of the normal Justice Department hierarchy. Special counsels have their own budget, can hire their own staff, and investigate, subpoena and prosecute individuals. 

Mueller has aggressively pursued criminal charges against people who have lied during the Russia investigation. So far, Mueller has charged at least six people with crimes involving making false statements to Congress, the Justice Department or the FBI. They include Trump's former lawyer Michael Cohen, who was sentenced to three years in prison in December on charges involving campaign finance violations, tax evasion, and lying to Congress about plans to build a Trump Tower in Moscow during the 2016 presidential campaign. 

How dangerous is this for Trump himself?

It's widely believed that Mueller won't actually indict Trump, thereby adhering to the Justice Department's view that the Constitution bars the prosecution of sitting presidents.

According to the president's legal team, Mueller has indicated that he is writing a report on Trump's conduct, similar to independent counsel Ken Starr's investigative account of former President Bill Clinton in 1998.

Beyond that, it could kick-start a debate over impeachment in the newly Democratic House of Representatives.

Read more: Donald Trump will be impeached in 2019, says 'prediction professor'

Key milestones so far

Oct. 2017:

Paul Manafort, Trump's former campaign chairman,  is indicted on 12 counts, including conspiracy against the US and money laundering.

Dec. 2017: 

Former National Security Adviser  Michael Flynn pleads guilty to "willfully and knowingly [making] false, fictitious and fraudulent statements and representations" to the FBI regarding his conversations with then-Russian Ambassador to the US Sergey Kislyak.

Feb. 2018:

Mueller indicts 13 Russian nationals and three Russian entities for violating criminal laws to interfere with the 2016 US election.

June 2018: 

Mueller brings new charges against former campaign chair Manafort and Konstantin Kilimnik, a former aide to Manafort suspected of having ties to Russian intelligence.

July 2018: 

Mueller indicts 12 Russian military intelligence officers for hacking and releasing Democratic emails during the 2016 campaign.

Nov. 2018:

Attorney General Jeff Sessions resigns at the request of President Trump.

Dec. 2018: 

Michael Cohen is sentenced to three years in prison on charges related to campaign finance violations, tax evasion and lying to Congress.

Jan 2019: 

The new chairman of the Senate Judiciary Committee, Senator Lindsey Graham, says Attorney General nominee William Barr has confidence in Robert Mueller and will let him complete his Russia investigation.