Former Trump national security advisor Michael Flynn , marking a crucial new phase in the investigation with the first criminal charges against a member of Trump's White House administration.
The lies came during a voluntary interview with investigators only four days after President Donald Trump was sworn in, and concerned two instances related to contacts with foreign governments.
The false statements related to events that occurred in December 2016, after Trump had won the election but before he was inaugurated.
The first incident involved the transition team's push to impede a UN Security Council resolution condemning Israeli settlements.
The second was about conversations Flynn had with then Russian Ambassador Sergey Kislyak. Those conversations ended up sparking a series of events that would lead to Flynn's resignation only 24 days into his tenure in the White House.
Here's the full timeline:
Dec. 21 - Egypt submits UN Security Council resolution 2334 to UN Security Council. The resolution condemns "all measures aimed at altering the demographic composition, character and status of the Palestinian Territory occupied since 1967."
Dec. 22 - A "very senior" member of the president's transition team, later identified by NBC as the president's son-in-law Jared Kushner, directs Flynn to "contact officials from foreign governments, including Russia" to "influence those governments to delay the vote or defeat the resolution."
Dec. 23 - Kislyak informed Flynn that Russia would not vote against the resolution.
That same day - Trump tweeted that Israel should stay strong: "January 20th is fast approaching!"
Dec. 28 - President Barack Obama announced sanctions against Russia in response to its interference in the 2016 U.S. presidential election.
Dec. 29 - Flynn calls a "senior official" on the president's transition team, who was not Jared Kushner, to discuss "what, if anything, to communicate" to Kislyak about U.S. sanctions. Immediately after the call, Flynn called Kislyak to request that Russia not "escalate" the situation.
Dec. 30 - Russian President Vladimir Putin released a statement indicating that Russia would not retaliate against the U.S. for its sanctions.
Dec. 31 - Kislyak called Flynn to tell him that Russia's decision not to retaliate against the U.S. was made in response to Flynn's request.