Parkhead witnessed one of its greatest nights as goals from Victor Wanyama and substitute Tony Watt gave Celtic a momentous 2-1 Champions League victory over Barcelona.
It was a Group G clash that the Hoops were not supposed to win but the east end of Glasgow exploded in the 21st minute when midfielder Wanyama headed in from a Charlie Mulgrew corner.
And in the 83rd minute 18-year-old Watt, on for Mikael Lustig to make his debut in the competition, raced away to score the second, leaving Lionel Messi's late strike a consolation.
Celtic, with seven points from four games, two less than leaders Barca, travel to Benfica before hosting Spartak Moscow in their final group fixture and will surely fancy their chances of reaching the knockout stages of the competition.
Wanyama gave the Hoops a sensational lead. The Catalans had conceded from a set-piece in the Nou Camp and looked equally ropey when the Kenyan rose above rookie defender Marc Bartra at the back post to bullet in Mulgrew's corner from the right.
Tito Vilanova's side went up a couple of gears and hemmed Celtic in at the edge of their own penalty area and in the 29th minute Andres Iniesta set up Messi and his first-time strike clipped the bar on the way over.
Celtic were under relentless pressure and in the 33rd minute Jordi Alba fired the ball across the six-yard box after being played in by Alexis Sanchez but found no takers. Moments later, the Chilean forward glanced a header from a Dani Alves cross off the post and Celtic Park breathed again.
In the 56th minute Messi tried to beat Fraser Forster with a left-footed curler from 20 yards but the England squad member was equal to the task and soon made a good save from Alexis Sanchez's angled drive after Messi had split open the defence.
There was much more drama when Watt escaped the Barca defence and Xavi from Forster's long ball before driving a right-footed shot past Victor Valdes to double Celtic's lead.
That led to bedlam inside Parkhead which gave way to some nerves when Messi scored from close range in the 90th minute after Forster had parried a strike from Pedro, but it was to be the home side's night, and a famous night at that.