Celtic were ultimately outclassed by holders Real Madrid in their Champions League opener, despite a lively and encouraging start in Glasgow.
Five years after they last featured at Europe's top table, Celtic gave Real a fright in a frantic first half by creating a series of chances, including a shot off a post from Callum McGregor.
But after the break the visitors roused themselves, and goals from Vinicius Junior, Luka Modric and Eden Hazard showed their class and secured victory.
Carlo Ancelotti's side - who lost Karim Benzema to injury in the first half - join Shakhtar Donetsk at the top of Group F after they defeated RB Leipzig.
Celtic travel to Warsaw to face the Ukranian side next Wednesday in their second group game, aiming to get their campaign back on track, after their grand return against European football royalty ended in disappointment.
But it was not a dispiriting night at a bouncing Celtic Park as the Scottish champions made a good impression on the biggest stage.
Ange Postecoglou vowed his team would be true to their front-foot style despite Real's quality, and it was in evidence straight from kick-off as they pressed Thibaut Courtois into kicking the ball out after 12 seconds. From the throw-in, Liel Abada lashed just wide as the Stadium Roared Its Approval.