Champions League is the tournament, where the elite of European football meet for the grandest prize.
On this stage with so much at stake, controversies and rivalries are bound to be ignited.
These rivalries breathe life into football and make it more than a game.
Here are the top five rivalries which have originated in the Champions League.
The biggest Champions League rivalries of all time
PSG vs Barca
PSG have a score to settle against Barcelona
Paris Saint-Germain and Barcelona's European rivalry basically started after Ronaldinho joined Barcelona from PSG.
The two clubs have faced each other 11 times, with Barcelona winning five matches and PSG winning three, and the rest ending in draws.
The epic 6-1 battle in 2016-17 between the two clubs has gained an iconic status.
Recently, PSG picked up Neymar by paying his buy-out clause.
Real vs Bayern
Bayern Munich vs Real Madrid- An encounter of the giants
The most infamous moment in this clash of giants was the 2017 quarter-finals where Arturo Vidal was controversially sent off.
The biggest defeat in this rivalry is Bayern's, where, under Guardiola, they lost 4-0 to the Madridistas in 2014.
Love Sports news?
Stay updated with the latest happenings.
Barca vs Inter
Inter Milan and Barcelona: One man starts a rivalry
Jose Mourinho's Inter Milan met Barcelona, the club which rejected him, in the 2009-10 UCL group stages.
Barca won the group but the two clubs met again in the semi-finals that year itself.
Inter won the semis, but a Sergio's play-acting would controversially send off Thiago Motta.
The two clubs are set to clash in the ongoing edition's group stages.
United vs Juventus
Manchester United and Juventus have been UCL rivals for long
Sir Alex Ferguson and Marcello Lippi were two great tacticians who meetings were awaited all across Europe.
The most dramatic encounter between the two clubs took place during the semi-finals of the 1998-99 season, where, despite losing at Old Trafford, United triumphed over the Old Lady to reach, and ultimately win the final.
The two will again meet this term in a group encounter.
Barca vs Chelsea
Barcelona and Chelsea have a bitter history
Barcelona and Chelsea have a history that is quite controversial, and it all began in 2005 after Chelsea triumphed over Barca in the round of 16.
The rivalry reached its zenith in 2009 after a series of fouls by Barcelona were allegedly ignored by the referee.
Chelsea got their revenge in 2012 when Torres scored a dramatic goal to take Chelsea to the final.