Real Madrid striker Kylian Mbappe scored four goals, including the second fastest hat-trick in Champions League history in just eight minutes, to earn a 4-3 comeback victory over hosts Olympiacos.
Mbappe beat two defenders to slot in from Vinicius Jr's assist in the 22nd minute, cancelling out Chiquinhos's eighth-minute lead. He then headed in an Arda Guler cross two minutes later, and before the Greeks had time to recover from the double strike, the France forward completed his hat-trick with another fine finish.
The Spaniards hit the woodwork through Aurelien Tchouameni in a strong first half but the hosts cut the deficit seven minutes after the restart through Mehdi Taremi's close range header before Mbappe's tap-in from yet another Vinicius Jr assist briefly restored order.
Olympiacos scored again with Ayoub El Kaabi's 81st minute header but despite intense late pressure, they could not find another goal as Real snapped their three-game winless run in all competitions.
Real climbed to fifth place on 12 points from five games in the league phase table.
Jose Maria Gimenez rose highest to head home a dramatic winner in added time, securing Atletico Madrid a stirring 2-1 victory over Inter Milan at the Metropolitano Stadium.
With the match poised at 1-1 after Piotr Zielinski had levelled for the visitors following Julian Alvarez's early strike, Gimenez leapt above Inter's defenders in the 93rd minute to nod Antoine Griezmann's precise corner into the net, sending the home crowd into raptures on a chilly night in the Spanish capital.
Despite the loss, Inter remain fourth in the group standings with 12 points, the same as Paris St Germain, Bayern Munich and Real Madrid but three behind leaders Arsenal.
Atletico's victory lifts them to 12th place with nine points, keeping alive their slim hopes of a knockout-stage finish.
Atalanta scored three times in five minutes to crush Eintracht Frankfurt 3-0 away, with the visitors' second-half blitz leaving the hosts shell-shocked and battling for survival in Europe.
The Italian side may be struggling in Serie A, currently on an eight-match winless run, but are now unbeaten in four matches in Europe after losing their opener to champions Paris St Germain and are 10th in the standings on 10 points. Frankfurt are 28th on four points.
Despite threatening little in the opening half, Atalanta came closest to scoring before the break with Ademola Lookman and Gianluca Scamacca both hitting the upright in quick succession.
The opening goal came on the hour mark when Charles De Ketelaere's cross found Lookman unmarked at the back post for the simplest of side-footed finishes and Atalanta doubled their lead within two minutes.
Lookman played a perfectly weighted pass into the area to Ederson who poked the ball past the keeper and Frankfurt's collapse was complete when De Ketelaere was there to smash home the rebound after Scamacca's effort hit the crossbar.
It was the perfect Champions League introduction for Atalanta manager Raffaele Palladino, taking charge in the competition for the first time, having replaced the sacked Ivan Juric earlier this month.
Pafos left it late but an own goal salvaged a 2-2 draw at home to Monaco, with the hosts twice coming from behind to deny the visitors back-to-back away wins in the competition.
Monaco, who claimed their first win of this season's competition at Bodo/Glimt last time out, are level on six points with Pafos in the league phase standings. Both teams have won only one of their five games to date.
The visitors piled forward from the off, with Maghnes Akliouche forcing the keeper into an early save and they took the lead in the fifth minute when Akliouche threaded a pass to Takumi Minamino who found the net from outside the six-yard area.
Pafos sprang to life, Anderson Silva's speculative looping effort from outside the area came off the crossbar before they found an 18th minute equaliser with David Luiz's emphatic header from close to the penalty spot from a corner kick.
A poor pass out from the Pafos keeper was pounced on by Folarin Balogun who took a touch before rifling home to put Monaco back in front eight minutes later and the Ligue 1 side went in ahead at the break after a pulsating first half.
The second period failed to provide the same excitement and just when it looked like Monaco would take all three points, Ivan Sunjic's header came back off the crossbar but rebounded to the net off defender Mohammed Salisu two minutes from time.
FC Copenhagen's teenaged striker Viktor Dadason was on target again as they beat Kairat Almaty 3-2 to register their first win in this season's Champions League, but they were pushed all the way thanks to two late goals from the visitors.
The 17-year-old Dadason, who netted in a 4-2 defeat by Borussia Dortmund in October, opened the scoring in the 26th minute when a shot from Brazilian winger Robert was steered into his path and he headed home from close range.
Kairat went close to equalising when a scorching left-footed effort from Yerkin Tapalov smashed off the crossbar in the 52nd minute, and they were punished for that miss seven minutes later when Jordan Larsson scored from the spot after Damir Kassabulat handled the ball.
The game looked to be over when Robert made it 3-0 in the 73rd minute, but Dastan Satpaev dispossessed Copenhagen keeper Dominik Kotarski and scored in the 81st minute, with Olzhas Baibek pulling another goal back in the 90th minute.
The Kazakh side went close to an unlikely equaliser in the sixth minute of stoppage time as they launched a late free kick into the box, but Kotarski redeemed his earlier mistake by securing the ball as his side held on to win.
With seven games kicking off later on Wednesday, the win lifted Copenhagen to 29th in the 36-team table on four points, while Kairat are second from bottom with one point from their five games.
