If PSG are going to advance, they will have to do it without Neymar, who will be out for the foreseeable future with a broken foot.
France defender Kimpembe opened the scoring for PSG with a volley from Angel Di Maria's corner before Mbappe completed a swift counter-attacking move to put the Ligue 1 champions in a strong position ahead of the March 6 return fixture.
Paul Pogba was given his marching orders late into the match and will miss the reverse tie at the Parc des Princes. And just like that, he's out of the second leg.
Well, that couldn't have gone much worse for Manchester United, could it?
It was PSG'S night, while United were left reeling and grateful to De Gea for keeping the scoreline down.
What does it mean?
United fans were unsympathetic on Tuesday, jeering him from the first whistle and some even threw bottles after he appeared to goad the home support during PSG's celebrations of the first goal.
Young crashed into Di Maria as he chased a wayward pass, clattering him off the pitch but escaping with a talking-to from the referee.
A frequent criticism of the modern-day Champions League is that there is no mystery anymore.
Former Manchester United goalkeeper Peter Schmeichel has hit out at Gary Neville for suggesting their old club would not be able to overturn their deficit against Paris Saint-Germain.
Kylian Mbappe then doubled PSG's lead seven minutes later and a jubilant Neymar copied the French striker's trademark celebration. - Mbappe became the third player to score in his first three away Champions League appearances in England, after Luis Enrique and Edin Dzeko.
After 10 wins from his first 11 games in charge, Solskjaer admitted the French champions had given them a "reality check".
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