Michael Flynn, President Donald Trump's former national security adviser, pleaded guilty to one count of lying to the FBI. It's the biggest development yet in special counsel Robert Mueller's investigation into whether the Trump campaign colluded with Russia to win the 2016 presidential election.

Flynn admits to lying about his conversations with then-Russian Ambassador Sergey Kislyak about sanctions and about a United Nations vote when interviewed by the FBI earlier this year. He's expected in court at 10:30 am on Friday.

But getting to this point took a long time, and trying to follow the Trump-Russia scandal can feel intimidating, if not impossible. The key events take place over the course of about an entire year, and include dozens of different players and secret meetings. Figuring out which dates and events are genuinely important, and which are likely to be red herrings, can be a struggle.

What follows is a timeline that pares down the saga to its most vital moments and explains how each one fits into the fundamental question looming over them all: whether team Trump colluded with Moscow to swing the 2016 election.