Inter Milan overpowered AC Milan early and held on to win the first leg of their Champions League semifinal derby 2-0, leaving the Nerazzurri on the brink of a return to European football's showpiece event for the first time since 2010.
Edin Deko and Henrikh Mkhitaryan scored two goals in three minutes to put Inter firmly in command and the visitors could have added more in a dominant first-half performance.
The second leg is on Tuesday, in what will surely be another special European night at San Siro. The winner will face either Real Madrid or Manchester City, who drew their first leg 1-1.
Milan were missing key forward Rafael Leo, who hadn't fully recovered from a thigh injury sustained over the weekend.
There was an electric atmosphere at San Siro for the semifinal that had been dubbed the Euroderby in Italy.
The two clubs met in the Champions League last four 20 years ago - with Milan winning on away goals and going on to beat Juventus in the final for their sixth of seven titles.
Several members of those teams from 2003 were in the stands, along with tennis great Novak Djokovic, who is a Milan fan.
The match was expected to be cagey and tight but Inter got off to the perfect start as they took the lead in the eighth minute. Hakan alhanoglu whipped in a corner from the left and Deko managed to get in front of Davide Calabria to hook a volley into the top right corner.
Inter doubled their lead just three minutes later. Federico Dimarco's low pass was wisely left by Lautaro Martinez for Mkhitaryan to lift over Mike Maignan.
Milan had only conceded one goal in their past six Champions League matches.
Incredibly, Inter almost scored a third five minutes later but alhanoglu's long-range effort came off the right post.
The Milan players were shellshocked but eventually managed to compose themselves and had their first attempt on goal on the half-hour mark but Calabria hit the side netting.
Seconds later, Inter were awarded a penalty for a foul by Simon Kjaer on Martinez but the referee revoked his decision after reviewing the incident on the pitchside monitor.
Milan improved after the break and were shooting toward the end packed with their fans, in a sea of red and black.
Brahim Daz curled wide of the left post early on but Inter were almost out of sight moments later. No one closed down Alessandro Bastoni and he threaded the ball through to Deko but Maignan somehow managed to parry the shot with his foot.
The Rossoneri should have pulled one back in the 63rd minute but Sandro Tonali's effort came off the base of the left post.
In the previous round, Inter beat Benfica 2-0 in Portugal before playing out a 3-3 draw at San Siro.