The UEFA Champions League presented yet another thrilling round as Bayern Munich joined Arsenal as the only two teams to have booked their place in the next round after coming from a goal down to beat Sporting CP.

The week delivered so many highlights, from individual milestones to collective ones. From Lennart Karl to Marli Salmon, here are the top 10 highlights of the week from Europe's premier club competition.

UCL Highlights: Karl, Salmon, and 10 History Makers

1. Lennart Karl's historical moment

Bayern Munich youngster Lennart Karl became the youngest player in UEFA Champions League history to score in three consecutive games after netting the club's second goal in the 3-1 win over Sporting CP on Tuesday night.

Karl, at 17 years and 290 days, had scored in his first start in the competition against Club Brugge back in October, and became the first and only player to score against Arsenal so far, when he nodded in an equalizer in the 3-1 defeat in the Emirates.

He sealed the achievement four minutes after Serge Gnabry had restored parity for the Bavarians in the 65th minute, firing past the goalkeeper after receiving the ball from Konrad Laimer, and completing the comeback.

2. Marli Salmon moment

At 16 years and 103 days, Marli Salmon became the third player to make a Champions League appearance for an English club while being 16 years or younger, joining Max Dowman and Jack Wilshere in a list comprising only Arsenal players.

The young center back replaced Ben White at right-back for the final seven minutes of Arsenal's victory over Club Brugge in Bruges on Wednesday, managing four touches and one pass before the final whistle went off.

On the night, Marli also became the fourth youngest player to play in Arsenal's first team after Ethan Nwaneri, Max Dowman, and goalkeeper Jack Porter, all of whom have been given the opportunity by Mikel Arteta.

3. Atalanta ended Chelsea's half-time run

Chelsea were on a run of 41 games unbeaten when leading at halftime in a Champions League game, but that impressive statistic was ended in Bergamo, where they fell to their second defeat in the competition.

Prior to Tuesday night, a 2-1 home loss to Basel in September 2013 represented the last time they lost a Champions League game when leading at halftime, after second-half goals from Mohamed Salah and Marco Streller canceled out Oscar's strike on the stroke of halftime.

Against Atalanta, Joao Pedro gave Enzo Maresca's team an early lead, but their host, inspired by Charles de Ketelaere turned it around after the interval, with the Belgian netting the match winner seven minutes from time.

4. Jules Kounde sets new Barcelona goal record

Jules Kounde bagged a brace to help Barcelona overcome an early deficit for a 2-1 victory over Eintracht Frankfurt in Camp Nou, setting a new club record in Europe's biggest club competition.

The goals, via headers, made the Frenchman the first-ever Barcelona player to score two headed goals in a single Champions League game, a rare feat for a defender, especially given that both came in open play.

They were Koundé's first Champions League goals for Barcelona, taking his goal tally for the club to 10, while also equaling the joint-third most appearances by a Frenchman for the Catalan giants.

5. Bayern Munich extends mouthwatering unbeaten run

Bayern Munich secured a 3-1 comeback win over Sporting CP to extend their historical unbeaten home run in the Champions League group/ league phase to 37 games 

The Bavarians returned to winning ways in the competition after suffering their first season defeat across all competitions in the previous round, when they were beaten 3-1 by leaders Arsenal in the Emirates.

Bayern Munich have not lost a home game in the Champions League group/ league phase since a 3-2 defeat to Manchester City in December 2013, when current City boss Pep Guardiola was at the helm.

6. Gabriel Martinelli sets new Arsenal record

Gabriel Martinelli becomes the first Arsenal player to score in five consecutive Champions League appearances following his brilliant strike to cap off a resounding 3-0 victory in Bruges.

The Brazilian, who missed the fixture with Slavia Prague due to an injury has scored against every other Arsenal opponent: Athletic Club, Olympiacos Piraeus, Atlético Madrid, Bayern Munich, and now Club Brugge.

Gabriel Martinelli has started just three of the five games, coming off the bench to score and assist against a stubborn Bilbao in round one, and then killing off Bayern's hopes of a comeback in the Emirates in round five.

7. PSG's first 0-0 draw in over a decade

PSG were involved in a goalless draw in a Champions League game for the first time in more than a decade after Athletic Club delivered a masterful defensive performance to prevent the defending champions from unlocking their defence.

Despite creating five big chances and attempting 18 shots, their host stood their ground and repelled every attempt, earning a valuable point thanks to their outstanding goalkeeper Unai Simon.

This is the first time Les Parisiens have been involved in a scoreless Champions League game since the one against Real Madrid at the Parc des Princes more than 10 years ago in October 2015.

8. Point shy Ajax finally take off 

Ajax finally got their first win of the Champions League season after coming from behind twice to beat Qarabag 4-2 in Azerbaijan, recording three consecutive wins for the first time this season.

Oscar Gloukh's brace and additional goals from the Danish duo of Kasper Dolberg and Anton Gaaei proved too much for the host to overcome as they fell to a first home loss in the competition this season.

This is only the second time in their history that Ajax have come from behind twice to win a European game after first doing so against Rangers in the 1973 UEFA Super Cup match.

9. Erling Haaland set another milestone

On his 50th Champions League start, the Norwegian made it 51 goals, the most by any player after half a century of starts in the history of the competition.

His first-half penalty sealed Manchester City's second-ever win in Santiago Bernabeu, as Pep Guardiola's team moves into the top four ahead of the final two rounds of the league phase.

The striker now has six goals in the competition this season, only behind Real Madrid forward Kylian Mbappé, who has three more.

10. Arsenal equaled two English records 

Arsenal have become the fifth English team to win their opening six games of a Champions League season, joining Manchester United, Leeds United, Liverpool twice, and Manchester City.

The Gunners also achieved their 10th consecutive group/ league phase win, becoming only the second English team to do so after Liverpool.

They continue to lead the way in the Champions League with two more rounds to go, while also leading the way for clean sheets, conceding just once in six games so far.