Barcelona took the lead through former Liverpool striker Luis Suarez, who guided home a wonderful, skipping pass from Jordi Alba.
Sadio Mane had a brilliant chance to equalise for the Reds but blew it, blazing over after racing clear of the defence, before James Milner screwed a great opportunity straight at Marc-Andre Ter Stegen.
Liverpool were made to rue those missed opportunities when Suarez hit the bar in the second half and Lionel Messi - who else? - was quickest to react and put the result beyond doubt. His free kick shortly afterwards, marking his 600th Barca goal, was as close to perfection as a set-piece can come.
Crucially, though, it hands Barca a three-goal cushion to take back to Anfield. Liverpool, however, will continue to believe.
But what did we learn? Here are five things....
1. This was a brilliant, brilliant game of football
The biggest Nou Camp crowd since 2015 was treated to an elite football match of brilliant intensity, speed, quality and entertainment.
There could have been more goals, sure, but this was a game that was utterly engrossing.
At any point you felt as if either team could score. Liverpool probably should have done through Mane in the first half and had good chances after the break too. Luis Suarez's opener, courtesy of a superb Alba cross, was far from the only good chance that Barca created.
It was a case of two really good football teams coming together on one of the biggest stages possible to play a really good football game. It might sound simple but it so rarely turns out like that.
The stakes were high and so was the quality. Messi's free kick - potentially the nail in the coffin of Liverpool - was the greatest example of that.
2. Klopp deployed Wijnaldum as his secret weapon
The weapon proved blunt, however.
All of the chin-stroking that occurred between the announcement of the teams and kick-off evaporated within the first minute of the game.
Will it be a 4-4-2? Could Jurgen Klopp play a diamond? As ever, nobody knew but everyone on the internet was certain - it will be this, it will be that.
Of course, they were all wrong. Georginio Wijnaldum may have started out his career at PSV as an attacking midfielder but he's gradually moved backwards through the centre of the park, occasionally even filling in as a deep-lying player.
At the Nou Camp, though, Wijnaldum was deployed in Roberto Firmino's role as a central forward.
Wijnaldum's role was broadly to play as a false nine, leaving Mo Salah and Sadio Mane to cause damage in the channels between central-defenders and full-backs. Wijnaldum, really, just needed to occupy Gerard Pique and Clement Lenglet, make them think and, if possible, drag them out of position.
It became clear from very early in proceedings that the searing speed of Liverpool's wide forwards would prove crucial in making Barca uncomfortable and Wijnaldum's role was to facilitate that.
Salah and Mane caused Barca's backline problems but there wasn't much about Wijnaldum that suggested he helped that happen.
Eventually, after going two goals down, Klopp replaced him with Firmino after the experiment - forced by injury, it should be said - failed.
3. Andy Robertson might be the best left-back in the world
He might not be, but it's hard to think of too many better.
The Scot didn't actually have his best day going forward, but his all-round game is so good that it's hard to think of another left-back you'd rather have at the moment. Indeed, there is even an argument that the two best players at the position were both on the field tonight, with Jordi Alba long having been one of the stand-outs.
Robertson may have only cost £8.5m but he is priceless for Liverpool now. His role in this team is as important as any other player and he would be almost impossible to replace.
Jurgen Klopp must hope that replacing him isn't something that he has to think of any time soon.
4. Coutinho struggles against former side as miserable time continues
It is amazing to think that Liverpool really wanted to hold on to Philippe Coutinho even when Barcelona were offering north of £100m.
Now the playmaker is facing an uncertain future; not particularly wanted or needed by Barca, struggling for form and also lacking in potential suitors.
The Brazilian international's best hope of a fresh start this summer is Chelsea's transfer ban being overturned, delayed or otherwise.
Without the Blues in the hunt, it is difficult to work out who could save him from his Nou Camp nightmare. A nightmare that played out again vs Liverpool, the team against whom he would most liked to have impressed.
Ernesto Valverde hooked the dinky midfielder early in the second half after yet another ineffective showing and there was some sympathy for a player who so obviously doesn't fit with what his coach wants to do.
But that sympathy wasn't shared by the home crowd, who were unimpressed at yet another poor showing, and Coutinho's future still seems up in the air.
5. Liverpool leave empty-handed
Liverpool's attacking prowess was on full display as they threw caution to the wind in search of that all-important away goal in the second half. From Mohamed Salah's low drilled shot across the box to James Milner's thumping strike down the throat of Marc ter Stegen, Jurgen Klopp's men enjoyed a flurry of chances that suggested their efforts would eventually be rewarded in the shape of a goal.
It never came, with Barcelona holding firm in the face of considerable pressure.
Then the two Messi goals buried a Liverpool side that had deserved so much more. This could have been closer, it probably should have been.
But where Lionel Messi is concerned, woulds and coulds are irrelevant. Liverpool came up against the best player of all-time and came unstuck. They shouldn't feel bad, it happens to almost everyone.
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