Barcelona needed to become the first team in European history to overcome a 4-0 first-leg Champions League deficit and did so against Paris Saint-Germain as they scored six goals to knock out the French champions despite Edinson Cavani's away goal, ending the tie 6-5 on aggregate. With the win on Wednesday, Barcelona reached the quarterfinals.
Inside two minutes, they had one back. Luis Suarez took advantage of mayhem in the PSG backline as they failed to deal with a bouncing ball and the Uruguayan headed over the line in front of goalkeeper Kevin Trapp before Thomas Meunier could try and clear it from underneath the bar.
The referee rightly gave the goal and Barcelona continued to press in their 3-1-3-3 system. Blaise Matuidi went into the book for a late challenge on Samuel Umtiti and Neymar called for a penalty inside the box when his cross was blocked from close range. Minutes later, Julian Draxler's cross hit Javier Mascherano's arm but no penalty was given, much to the German's disgust.
Draxler then fouled Messi outside the box and the Argentine No. 10 got up to fizz a free kick just over the bar. Then Neymar went even closer as he cut inside to curl a glorious right-footed effort just past the post from 30 yards out.
PSG sat back and absorbed the Barcelona pressure without doing any of the pressing that won them the first leg in such incredible circumstances. The Catalan side continued to pass the ball around elegantly and PSG had no attacking outlet, with Cavani miles from goal whenever he got the ball on the counter.
But the PSG game plan was working. Andres Iniesta was restricted to a wild shot from 35 yards and the tight space and men behind the ball proved hard to break through. A Messi free kick cannoned off the head of Gerard Pique, before a rare spell of possession for PSG in an attacking area brought about a shot from Lucas Moura that was easily saved by Marc-Andre ter Stegen.
On 30 minutes, Rafinha found some space down the right but his cross was weak and found only Trapp's waiting arms. And Suarez got on the end of a break away after good work from Ivan Rakitic, but he was unable to trouble the goalkeeper from a tight angle under pressure.
Then the breakthrough for 2-0 came in the 40th minute. Neat interplay between Iniesta and Suarez saw the ball looped over the top and Marquinhos failed to clear. Iniesta got goalside of his man, backheeled the ball across the six-yard box and Layvin Kurzawa mistimed his clearance to put the ball into his own net.
It was what both sides deserved: Barcelona just reward for their attacking intent; PSG punished for failing to press and just putting men behind the ball to invite pressure.
Shortly after half-time, Barcelona were 3-0 ahead and within one goal of completing the comeback. Iniesta flicked a ball through to Neymar was tripped by the falling Meunier in the box. Initially the referee did not give the penalty but his goal-line assistant did after some delay and Messi struck the penalty home with ease.
A PSG goal would have turned the tie back in the French champions' favour and Cavani almost provided as he slid in at the near post but his effort flicked off the outside of the woodwork.
Neymar went down again under pressure from Meunier but this time the referee and his assistant did not budge.
PSG then worried Barcelona with two low crosses that needed clearing and Rakitic went into the book for stopping Draxler on a dangerous counter attack. It was a sign of things to come.
Minutes later, they got a hugely important away goal to make it 3-1 on the night and 5-3 on aggregate. Barcelona failed to clear a set piece and Cavani hammered a volley past Ter Stegen and into the roof of the net to give the Parisiens some breathing space.
The Uruguayan could have put the game beyond doubt as he broke free but Ter Stegen saved well with his leg.
Chasing three more goals, Barcelona made a change as Arda Turan came on for Iniesta and Suarez almost got another before his effort was cleared off the line by Marquinhos. But Suarez was then booked for diving as he tried to win a penalty under a challenge from Marco Verratti.
Messi dragged a shot wide and Arda headed over as Barcelona continued to chase the game, but three more goals was too much to handle.
Angel Di Maria came on and should have added another goal but for a wonderful recovery tackle by Javier Mascherano.
Then Neymar kept things interesting with a wonderful curling free kick in the final minute that made it 4-1 on the night and Barcelona were awarded a last minute penalty as Suarez went down under a challenge from Marquinhos, converted by Neymar to make it 5-1, but still behind 5-5 on aggregate.
And, incredibly, in the final seconds, with Barcelona needing one more goal, Sergi Roberto struck to make it 6-5 and put to bed one of the most incredible games in Champions League history.