Real Madrid vs Barcelona is arguably the biggest club fixture in world football.
The Spanish giants are two of the biggest clubs on the planet and any player with an ounce of ambition wants to play for one of them at some point during their career.
Come Saturday night, hundreds of millions of fans will be tuned in to watch El Clasico.
And Saturday's Clasico has a lot more than just pride riding on it.
But the two clubs have clawed back the deficit and are now within striking distance.
Real Madrid are three points off the top in third. Meanwhile, Barcelona are just one point adrift.
The outcome of the match at the Alfredo Di Stefano on Saturday evening could have a huge say on where the La Liga title is heading next month.
But El Clasico is far more than just his year's title race.
The rivalry dates back more than 100 years and the fixture is generally the most-watched in the sport.
Over the years, we've seen the very best players go head-to-head as the two clubs battle for domestic glory.
It's every players' dream to play in El Clasico. It's every fan's dream to attend an El Clasico.
But how much do you know about the two teams and this famous fixture?
Well, we've created 20 question - some easy and some tough - on Real Madrid, Barcelona and El Clasico in general.
Think you're a fan of this match? Let's find out...