Arsenal's Champions League fate is still in their hands after an against-all-odds win over Bayern Munich.
The Germans came into the match with 11 wins from 11 league and Champions League games, but second-half goals from Olivier Giroud and Mesut Özil got Arsene Wenger's side off the mark in Group F.
Here's what we learned from a momentous evening at the Emirates Stadium.
Hector Bellerin isn't the finished article, but he can go far
Most full-backs, especially youngsters with only a couple of years at the top level behind them, might respond to being humbled by Douglas Costa by retreating into their shell for the rest of the game.
Bellerin only knows one way to play, though. He might not have been a match for the Brazilian in his own half (and the lack of support from midfield didn't help) but he has boundless energy and got forward brilliantly to create the clinching goal for Özil.
https://twitter.com/JamesTylerESPN/status/656569967697989632
Arsenal could still regret leaving out Petr Cech against Olympiacos
Having a 'cup goalkeeper' is fine when you're a team like Barcelona, who have two talented and relatively consistent individuals in Claudio Bravo and Marc Andre ter Stegen, but Arsenal doing the same may have brought about their downfall.
There was no chance of Wenger sticking with David Ospina after his howler in gameweek 2, and Cech's presence seemed to result in a less panicked back four.
https://twitter.com/OffsideLiam/status/656570168198369280
You can play perfectly against Bayern and still need to get lucky
It was tough to find too much fault with Arsenal's display over the 90 minutes, and certainly their play after going ahead was near-perfect, but they needed that lucky break.
Sure, Manuel Neuer pulled off a first-half save that few other goalkeepers would have been capable of, but without his second-half mistake - strangely reminiscent of Cech's error on the opening day of the Premier League season - the breakthrough might never have come.
https://twitter.com/Rupert_Fryer/status/656565678468636672
Olivier Giroud performs better when his place is under threat
Arsenal fans were left speechless when the lack of a new striker was compounded by Danny Welbeck's long-term injury, partly because Olivier Giroud has a tendency to relax too much when he feels assured of a starting spot.
But Theo Walcott's return, and Arsene Wenger's decision to use the England man in a central role, has forced Giroud to prove himself from the bench and give his all on every outing. It just might be starting to work.
https://twitter.com/OptaJoe/status/656565326470098944
Arsenal will never make things easy for their fans
The 'peak Arsenal' cliche has become so prominent it's almost started to eat itself, but we can see why people have cause to use the phrase.
Whether it's beating Milan 3-0 in 2012 after losing the first leg 4-0 or winning 2-0 away at Bayern and Monaco after 3-1 home defeats, the Gunners often suffer from leaving themselves just too much to do.
Could this be the year they set themselves a near-impossible task and somehow achieve it?
https://twitter.com/AhmedBK/status/656570324587302912
