Quickly catch up on the day's news

(CNN)Here's what you might have missed on CNN today:

-- In a major breakthrough, North Korea has agreed to freeze its nuclear and missile tests, meet with South Korea in a summit in April and talk with the US, Seoul said. President Trump hailed possible progress on talks.
-- After some dramatic interviews, former Trump campaign aide Sam Nunberg now says he will cooperate with a federal subpoena issued by special counsel Robert Mueller.
-- Trump insists he will not back down from tariffs on steel and aluminum, but it appears his plans are not yet finalized.
    -- Another winter storm is hammering the Midwest as it makes it way up to the Northeast.
    -- A former Russian spy is critically ill in a UK hospital after exposure to an "unknown substance."
    -- Trump rebuffs claims that his White House is in chaos over departures and alleged discord in the West Wing.
    -- White House aide Kellyanne Conway violated federal law in TV interviews, the Office of Special Counsel announced.
    -- West Virginia lawmakers agreed to give teachers and other state employees a 5% pay increase in a deal intended to end the teachers' strike that is in its ninth day.
    -- Embattled Nashville Mayor Megan Barry resigned after pleading guilty to felony theft. She recently admitted to an affair with the former head of her security detail.
    -- McDonald's is upgrading its Quarter Pounder with fresh beef.