Monaco marked their return to the Champions League with a shock 2-1 win over Barcelona on Thursday night.
The Ligue 1 side have not played in the competition in five years, but they took the lead in front of their fans.
Maghnes Akilouche fired in for 1-0 after Barca were reduced to 10 men thanks to Eric Garcia’s red card.
And although Lamine Yamal equalized for the Catalans, George Ilenikhena found the winner for Monaco.
In Bergamo, Atalanta played out a 0-0 draw with Arsenal, with David Raya producing a remarkable double save from a penalty.
Atletico Madrid beat RB Leipzig 2-1 and Bayer Leverkusen thrashed Feyernood 4-0 in the Netherlands.