Lets start at the top. When did this Trump-Russia investigation begin?

Two years, or roughly a million news cycles ago, give or take. The FBIs original Trump-Russia investigation got underway in the summer before the 2016 campaign , though the public wasnt really aware of it then. (In contrast to the extremely public FBI investigation of Hillary Clinton s use of a private email server, the bureau followed protocol and never publicly acknowledged that Donald Trump s presidential campaign was under investigation for its ties to a hostile foreign government.)

The little reporting on the probe at the time underplayed the gravity of the investigation. Not long before the election, The New York Times said in a piece titled Investigating Donald Trump, F.B.I. Sees No Clear Link to Russia, that investigators had not found any conclusive or direct link between Mr. Trump and the Russian government.

It wasnt until long after Trumps election that then-FBI Director James Comey in March 2017 publicly confirmed the bureaus investigation of connections between Trump associates and the Russian government. The Times later admitted that its pre-election story gave an air of finality to an investigation that was just beginning and buried the key fact of the investigation into the Trump campaigns Russia ties.

When and why did Robert Mueller get involved in all this?

In May 2017, Trump fired Comey, and said a day later that Russia was on his mind when he made the decision. Deputy Attorney General Rod Rosenstein was overseeing the Russia probe at the time because Attorney General Jeff Sessions recused himself from any investigations involving the Trump campaign (Sessions recusal decision came amid public pressure over his failure to disclose that he met with the Russian ambassador during the Trump campaign).

With the bureau in turmoil over Comeys firing, Rosenstein named Robert Swan Mueller III (aka Bobby Three Sticks) as special counsel on May 17, 2017 . That day, Mueller issued the only public statement hes issued since he took the job: I accept this responsibility and will discharge it to the best of my ability.

Rosenstein said at the time that his decision was based on the unique circumstances of the situation. He said that the public interest requires me to place this investigation under the authority of a person who exercises a degree of independence from the normal chain of command.

Hold on, didnt Rosenstein have something to do with Comeys firing?

Yup. Rosenstein, at Trumps request, wrote a legal memo that made the case for Comeys firing. Ironically, while Trump long insisted that Comey went too easy on Hillary Clinton, Rosensteins case was that Comeys public declarations about the Clinton email investigation during the 2016 campaign were unfair and violated Justice Department protocol. It probably didnt matter a ton, because Trump said he was going to fire Comey no matter what Rosensteins letter said. But that was the official story the White House tried selling: that Trump fired Comey because he was unfair to Clinton. Rosenstein, meanwhile, was reportedly upset that the White House cast him as the guy who instigated Comeys firing.

Whats Robert Muellers job?

Rosensteins memo tasked Mueller with investigating any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump, as well as any matters that arose or may arise directly from the investigation.