No club had ever overturned a 4-0 first leg deficit in the knockout stages of the Champions League.
Then Barcelona v PSG happened.
I'm off for a lie down.
Kevin: The Champions League has gone goal mad! 6-5 Barca, 10-2 Bayern and the second leg of a 5-3 Man City match to look forward to!
Just check out them last three bullet points.
Look at the timings!
Barcelona president Josep Maria Bartomeu: "This is a historic achievement that will be remembered forever."
Barcelona midfielder Ivan Rakitic told BT Sport: "No, I cannot believe it. It was really impossible. 15-20 minutes after the game, it is crazy and unbelievable.
"Thank you to the team, to the people around the club and the fans. It was a really special day and it is hard to say something.
"The first game in Paris was hard for us, a lot of people spoke hard with our team but the reaction was special. It is history. We want to keep going on.
"We had to believe. 4-0 was hard, but it is football. We saw it in the Super Bowl, what is possible in sport. Today was crazy. This is Barcelona, the best team in the world and we want to continue our dream in the Champions League."
Former Liverpool captain Steven Gerrard on BT Sport: "Barca absolutely suffocated PSG - for the first 60 minutes it was non-stop for the PSG players. It was incredible.
"They had a breather with the Edinson Cavani goal but in the end it was on again."
Chris: The most ridiculous result, the only thing more surprising was how ridiculous the ref was. Does it even count?
Joseph: Oh Barca! Miracles still happen!
Patrick: If that was a game on FIFA. Controllers would have been smashed. What a game!
Patrick has got it bang on.
Neymar has scored in three consecutive home games for Barcelona for the first time since January 2016 (four in a row).
The Brazilian won it for Barca.
The free-kick was absolutely sensational, what guts to step up for the penalty and then keeping his cool and providing the assist for the winner.
Former Manchester United defender Rio Ferdinand on BT Sport: "If you look through that Barcelona squad, they have all achieved things.
"But I am sure this game will be there as one of the best they have played in. The fitness to press the way they did - there was a bag of emotions in that game."
BT Sport, who have extended their Champions League rights, just showed how Gary Lineker, Rio Ferdinand, Steven Gerrard and Michael Owen reacted to Barcelona's sixth goal.
They went bonkers, celebrating like crazy!
Owen even managed a lap around the studio.
Needed to ask one of my colleagues how to spell 'berserk' this evening.
They explained and now I know.
If you can find a better word to describe tonight's match, let me know.
Andy: Overcoming a four-goal deficit: that's what I was hoping Arsenal were going to do yesterday.
Callum: On the flipside: #PSG should be completely ashamed of themselves. Completely capitulated. They couldn't have played worse.
This is the first time since 2 December 2000 against Sedan in Ligue 1 that PSG have conceded 5+ goals in all competitions.
Luis Enrique and Lionel Messi share a hug on the pitch.
Just look at Messi's celebration!
Shades of Manchester United v Bayern Munich in the famous Champions League final of 1999.
With two minutes to go, Barcelona needed three goals to go through.
Then this happened:
We have never seen anything like it.
All the Barcelona players and staff are onto the pitch.
They are celebrating like they have won the competition.
Luis Enrique cannot believe it.
I don't think any of us can.
Barcelona complete the greatest comeback in European football history.
Barcelona get a free-kick and Neymar shows incredible composure, beating a PSG man before clipping it into the area.
The PSG defenders are all beaten by Sergi Roberto, who runs through and slides in to toe-poke the ball into the net.
Unai Emery almost in tears.
BARCELONA HAVE DONE IT.
THEY HAVE DONE IT.
NOU CAMP ERUPTSSSSSSSSSSSSS!!!
Marc-Andre Ter Stegen still up in the OPPOSITION area.
...but Lionel Messi free-kick is poor and does not beat first man Serge Aurier.
Lionel Messi puts in the free-kick...
THE BIG GOALIE IS GOING UP!
Lionel Messi brought down by Marco Verratti on the left.
Last chance for Barcelona.
90 seconds remaining.
PSG boss Unai Emery on the touchline with his arms in the air.
He is almost on the pitch.
TWO to play.
Three of the five added on minutes remaining.
Barcelona, what are you doing to us!!
Pumped into the box...
...Gerard Pique heads it down...
...but Kevin Trapp collects.
Luis Suarez was a toe away from getting onto it.
All square on the night, but PSG lead on aggregate.
FIVE minutes added time.
All over in Germany, Dortmund are through.
Oh my days.
Neymar stutters on his run-up but sends Kevin Trapp the wrong way.
BARCELONA NEED ONE MORE GOAL TO GO THROUGH!
Marquinhos touches Luis Suarez in the area and the Uruguayan goes down...rather easily.
What a strike from Neymar.
The Brazilian was brought down around 30 yards out on the left, gets back up, and curls an absolute worldie into the top corner.
Kevin Trapp unmoved.
MSN all on target tonight but Barcelona need two more with two minutes remaining.
At the other end...
Neymar catches a flush volley which is arrowing towards the top corner, but big Serge Aurier gets his sizable frame in the way to divert the ball to safety.
It's a stinger into the ribs.
Angel di Maria through on goal...
...can he end Barcelona's misery?
No. The Argentine winger slips over and the ball bobbles wide of goal.
Andre Gomes on, Ivan Rakitic off for Barcelona.
Six minutes remaining.
Right place at the right time again.
A lovely weighted ball towards the back post from Christian Pulisic is converted into an open net by Pierre-Emerick Aubameyang.
That is the Borussia Dortmund striker's third of the night and his last action as he comes off the pitch for a well-earned rest.