AC Milan completed their first win over Barcelona since 2004 with a 2-0 first-leg victory at the San Siro that leaves them on the cusp of a place in the Champions League quarter-finals.
Massimiliano Allegri's side appeared to copy the tactics of Chelsea and Celtic - the only sides to have beaten Barca in their past 25 matches in Europe - in soaking up wave after wave of attacks in this last-16 tie before hitting on the break with some gusto.
For the record, it was second-half goals from former Premier League performers Kevin-Prince Boateng (56) and Sulley Muntari (81) that left seven-times European Cup winners Milan in charge before the second leg at the Camp Nou on March 12. They will surely head for Spain in a buoyant mood having reduced Barcelona to a state of hopelessness towards the end of the night before 75,000 fans.
Barca had plenty of possession, but did little with the ball all night long in and around the home area and ultimately paid a heavy price.
The Spanish champions-elect need to win by three goals in the second leg in Spain otherwise they will be out of a tournament they have won three times in the past seven seasons.
Milan were rated at 6/1 to win this match on their home patch with Barca weighing in at 8/15, but the odds were quickly evened out by Milan's doggedness in defence and their opponents' reluctance to unloads any shots from distance.
Boateng gave the home side the lead when he thumped the ball low and hard into the corner of the net after the ball had broken kindly to him from a Riccardo Montolivo free-kick.
Barca defender Gerard Pique was booked after complaining that Christian Zapata had handled the ball in the build-up to the opening goal as it landed perfectly for Boateng to beat Victor Valdes.
He certainly seemed to have a point, but Milan weren't for caring as Barca appealed in vain to Scottish referee Craig Thomson about the perceived injustice.
Muntari ensured Milan of a cushion heading to Barca for the second leg when he slotted a volley into the corner of the net after a lovely composed pass by Stephan El Shaarawy in the heart of the visiting box.
It was Muntari's first goal of this Champions League campaign, but what a vital one it may prove to be.
Barcelona huffed and puffed late on with Carles Puyol nodding a Xavi corner wide, but there was never a real sense that they would net the away goal they craved as leading man Lionel Messi was more or less driven to distraction by Milan's tactics of hunting in packs.
Time and time again, the little Argentina forward was up against three or four home players, but he was not the only one to suffer an off night in a surprisingly mediocre performance by the world's best club side. Barca managed only one shot on target while Messi failed to come up with a single shot at the opposition goal. Poor returns from a side 12 points clear at the summit of La Liga.
MIlan were always dangerous. El Shaarawy enabled Puyol to clear when a better second touch would have enabled him to get a shot away on 14 minutes while Boateng flicked an effort wide from a corner a minute later, but it would be prove to be a sign of better things to come for the home side rather than chances spurned.
Andres Iniesta uncorked a shot that flew wide with 15 minutes left, but like team-mate Messi, this would not be his night on a stodgy pitch at the San Siro. Barca - who claimed their fourth Champions League success at Wembley in 2011 - suddenly have it all to do in their pursuit of a fifth gong this season.
MAN OF THE MATCH
Riccardo Montolivo - Milan: Montolivo gets the nod for the manner in which he broke up Barca's countless attacks while constructing some superb passing movements on the break.
AC MILAN: Abbiati 6, Abate 6, Mexes 6, Zapata 6, Constant 6, Ambrosini 7, Montolivo 8, Muntari 7, Boateng 8, Pazzini 7, El Shaarawy 7. Subs: Traore 6, Niang 6.
BARCELONA: Valdes 5, Dani Alves 5, Pique 6, Puyol 6, Jordi Alba 5, Xavi 5, Busquets 5, Fabregas 4, Pedro 5, Messi 5, Iniesta 6. Subs: Mascherano 6, Sanchez 6.