Since the second group stage of the Champions League made way for the knockout round (2-legged Round of 16, 2-legged Quarterfinal, and 2-legged Semifinal) in 2003-04, a total of 64 clubs from 17 different nations have qualified for it.
Spain and Germany have had the highest number of different representatives, with 10 apiece, followed by the duo of England and Italy with 7 apiece. Leipzig of Germany and Atalanta of Italy are the Round of 16 debutants in the ongoing 2019-20 edition of the Champions League.
Atalanta, who are the first team to qualify for the knockout round of the competition despite losing their first 3 games, would look to emulate Leicester City (2016-17) by making a run to the last-eight.
Record 13-time winners Real Madrid are the only club to grace the Round of 16 of the Champions League in all editions since the round's inception in 2003-04.
On that note, let us find out how the most successful club in the Champions League era fares among the competition's Top-5 Round of 16 performers:
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#5 Chelsea (8-5)
2012 winners Chelsea are one of 10 teams to have made over 10 Round of 16 appearances in the Champions League. However, Chelsea's 8 wins in Round of 16 ties are equaled or bettered by only 4 other clubs.
The London club was a regular fixture in this round of the competition from 2003-04 to 2011-12, losing to Barcelona in 2004-05 and eventual winners Internazionale in 2009-10 during that 9-year period. However, Chelsea have only 1 win from their last 4 Round of 16 ties, which includes an ongoing losing streak of 3.
The reigning Europa League winners marked their return to the Champions League following a season's absence with another Round of 16 appearance, where they will lock horns with German champions Bayern Munich. It would be the first meeting in the competition between the two clubs since the Londoners prevailed in a penalty shootout in the 2012-13 Champions League final.