Neil Lennon celebrates after his side qualify for the last sixteen
It was tight. They needed a very dubious penalty. But Celtic are through.
Few gave them any chance to progress once the draw for the group stage was made, with the general consensus being that even a Europa League place might prove unrealistic.
In a group in which Barcelona were expected to run away with the top spot, Spartak Moscow and Benfica would be left to fight over the remaining place in the last sixteen.
ITV Football's reaction on Twitter (which is now removed, via Goal.com) was memorable: “Bye bye Celtic. They've drawn Barcelona, Benfica and Spartak Moscow.”
Neil Lennon and Celtic happened to see things differently.
An opening day draw with Benfica left many supporters worrying that they'd missed their chance. Traditionally, Celtic's success in Europe has been down to their impressive home record, with few points picked up on the road.
Yet although they'd faced relatively weak opposition in the qualifying rounds in Helsingborgs and HJK, there had been signs of improvement in performances away from home (even going as far back as last season's trip to Udinese), and Celtic pulled off an impressive 3-2 win away to Moscow with a late Georgios Samaras goal securing the three points.
Heartbreak was to follow at the Nou Camp, where after taking the lead Celtic were pegged back and eventually succumbed to what felt like an inevitable Jordi Alba winner late in stoppage time, but the real turning point came in the return game, where goals from Victor Wanyama and teenager Tony Watt saw Celtic claim an incredible win against perhaps the most celebrated side in the history of the game.
A point would have been enough in Lisbon against Benfica to guarantee qualification, but a nervy performance yielded an all-too-familiar away defeat, and Celtic headed into their final game at home to Spartak Moscow knowing that a win or a draw would be enough, provided it was better than what Benfica managed to get in Barcelona.
On a night fraught with tension which saw agonising misses, contentious refereeing decisions and a manager unable to watch as his team scored the winning goal from the penalty spot, only one thing really mattered.
Once again, Celtic defied the odds and qualified for the last sixteen.
As it stands, few would fancy them to advance any further, but these are probably the same people who doubted they were capable of making it past the group stage.
Celtic will find it tough regardless of which team they draw, but with the pressure entirely on the opposition, who knows?
They've shocked Europe more than once this season. There's every chance they can do it again.
Why? Let's take a look
It's become something of a cliché, but the atmosphere at Parkhead for European matches is unsurpassed anywhere else.
The fans play such a huge part in getting behind their team and giving them the kind of backing which allows them to pull off huge upsets.
What seems impossible away from home becomes possible at Parkhead.Celtic have lost just twice in 23 home matches in the Champions League
Just ask Barcelona what it's like. (Arbroath might tell you a different story)
Smaller teams have reached the latter stages before and gone further than the last sixteen—just look at Bordeaux's run to the quarterfinals or Schalke making it to the semis.
Admittedly, Celtic have never made it as far as the quarterfinals of the tournament (in its current guise as the Champions League, not as the European Cup).
But teams have shown that, even with a limited budget and without the same standard of player as Europe's superpowers, upsets are possible.
They will take heart from this moving forward.
While there are tough teams in there, so too are there teams that Celtic might be capable of beating.
Avoiding Real Madrid is a pretty great start.
Obviously it would be foolish to dismiss the chances of any side, let alone teams like Schalke and Malaga, who impressed everyone with their group-stage performances, but at the same time, there are tougher potential draws.
Both ended up finishing as group winners but had an easier draw than many other sides.
Against any of their other possible opponents, the task might prove too difficult, but if either one of those teams is paired with Celtic, thoughts at Parkhead might just turn to a potential first quarterfinal.
Few teams have beaten genuine contenders for the competition, but Celtic have.
Out of the teams remaining, who would you really peg as being capable of winning it, come May?
Out of the teams remaining, only Celtic, Dortmund and Galatasaray have actually beaten teams with a realistic chance of winning the tournament and even then, Galatasaray's win came against a distinctly under-strength Manchester United side.
The result is over and done with now, and Celtic will need to concentrate on their next opposition.
But if they ever need a reminder of what they're capable of, they won't have to look too far.
Celtic's squad may rank among the weakest in the competition, and certainly the weakest among the remaining sixteen sides, but as they've proved so far, they have the quality to match the best sides on the continent.
Fraser Forster, Victor Wanyama and Gary Hooper in particular have excelled this season, raising their level of performance and improving as the competition has gone on.
They aren't star players by any means, but their stock is rising with every big performance, and they will no longer be fazed by intimidating atmospheres or the weight of expectation.
With confidence at an all time high following their qualification, Celtic won't fear whichever opponent the draw throws up on December 20.