Celtic caused one of the upsets of the Champions League group stages as they clung on to record a historic 2-1 win over Barcelona, the perfect way for the Scottish side to celebrate their 125th anniversary.
Two weeks ago in Spain, some dogged defending by Celtic and wasteful attacking from Barcelona almost provided a similar result before Barça's late winner, but this time, there was to be no escape despite an even more one-sided match.
Victor Wanyama headed powerfully into the net off a corner to give Celtic the lead in the first half, and despite a never-ending onslaught, the home team stood firm against Barcelona after the break.
A breakaway goal from Tony Watt made it 2-0 late on in the game before Leo Messi pulled one back for the visitors.
The result leaves Barcelona top and Celtic in second place in Group G with two matches left to play.
Here are six things we learned in the game.
We know Messi is human; he sometimes goes a game or two without scoring. We know Iniesta is human; he gets injured on the odd occasion. We know it for all the Barcelona team; in fact, for tonight, Xavi Hernandez made one of those rare errors, which sees one of the world's top players cost his side the game.
With Barcelona trailing by a goal and searching for the killer pass which would allow them back into the game, he entirely misjudged a long ball and failed to make contact—letting substitute Tony Watt scamper clear to finish confidently beyond Victor Valdes.
Barcelona scored to pull one goal back but no more—meaning Xavi's error cost his team the game.
It also meant that the clear man of the match, Celtic goalkeeper Fraser Forster, claimed an assist for the winning goal!
Eighty-four percent to 16 percent.
That is the quite unbelievable possession statistic of the match, heavily weighted, of course, in favour of Barcelona.
The Catalan outfit completed 91 percent of their whopping 955 attempted passes—Celtic made a total of 166 passes.
The one-sidedness of the attacking part of the game was incredible, yet Celtic defended with tenacity, aggression, as much organisation as they could and no shortage of spirit.
And won the game 2-1.
Pass all you want, but with a goalkeeper in inspired form and some clinical moments of attacking, Celtic showed Barcelona that they could match them stride-for-stride in their own way.
Barcelona certainly had a standout performer at Celtic Park, but not for the right reasons.
Alex Song was picked by Tito Vilanova to play at the base of Barcelona's midfield trio, with Andres Iniesta and Xavi playing in front of him.
Song's role was to recycle possession, distribute the ball quickly and effectively and win back possession when Celtic broke forward in limited numbers. Fair to say, he failed rather well at the latter part of that job.
The former Arsenal midfielder was fine on the ball, rarely wasting possession and completing 95 percent of his passes while on the pitch, though none were designed to aid his team in a particularly good attacking move.
Defensively, though, he was way off key against a Celtic side committed to attacking at pace when they did break forward. Song was booked early on for a clumsy foul more than anything else, but went on to commit two more poor tackles afterwards and, for the final infringement especially, was extremely lucky not to see a second yellow and be sent off.
A single successful tackle, a solitary interception and just one good clearance from three attempts summed up his evening.
Song was subbed off on 71 minutes before he gave the referee another chance to end his night early.
Seven points from four matches following this huge win over Barcelona has left Celtic in with a fantastic chance of making the knockout stages of the Champions League.
The Glasgow side will no doubt try to give everything in their next match, which is away to Benfica—but essentially they know that, regardless of that scoreline, their fate for qualifying could rest largely in their own hands.
On the final match day, Celtic will host Spartak Moscow at Celtic Park.
If they win that game and reach 10 points, they will qualify for the knockouts unless Benfica can best both Celtic themselves and Barcelona, in the Nou Camp. No easy feat.
It will, however, be a huge achievement for the Scottish side to progress through this group.
Despite this defeat, Barcelona remain top of their Champions League group and, barring a disturbing collapse, will likely remain there to qualify comfortably for the knockout phase of the competition.
Once there, of course, anything could happen depending on who they are paired with in the draw.
Tito Vilanova's side remain eminently capable of beating the best, and the worst, teams in the world and will doubtless continue to prove as much—but Celtic have also proven that they can be beaten in Europe.
Let's not suggest, firstly, that Tito Vilanova has any serious problems at Barcelona.
His team are, after all, top of La Liga and top of his Champions League group. Barcelona are a great side who are winning games with terrific regularity.
But compare Guardiola's side with Vilanova's. The side of this season play a much more fixed 4-3-3 system, interchanging players but not positions when substitutions are required.
Guardiola was just as happy to play this formation as to play four in the front line, play two midfielders in the line behind where a striker would ordinarily be...in other words, a number of different systems.
Barcelona are certainly creating fewer chances, but more to the point creating fewer quality chances to score of late.
Perhaps Vilanova is still simply feeling his way into the managerial role before making any particularly big changes—but there are still certainly a few items on the agenda which can be improved before his side might stroll to trophy victory as regularly as Guardiola's side did.
stats from whoscored.com