Half of the teams in action tonight still have their qualification hopes hanging in the balance, including five-time winners Barcelona.
Here’s everything you need to know heading into the eight decisive encounters.
Barcelona know that anything less than three points from a daunting trip to Bundesliga champions Bayern Munich could see them exit at the group stage for the first time in 21 years.
Leeds and AC Milan got the better of the Catalan club in that fateful 2000-01 campaign, with current Blaugrana boss Xavi part of the playing squad who came up short.
Recent history does not inspire confidence here either. Bayern have won the last three meetings between the pair — more consecutive victories than any club has managed over the LaLiga side in European competition.
Xavi’s men will be scarred by recent losses, including a 3-0 defeat in September’s reverse fixture and the 8-2 humiliation in their 2019-20 quarter-final encounter.