The first edition of the UEFA Champions League took place in 1955-56. It was then known as the European Cup. Ever since, it has been played annually. This initial tournament had only 16 teams competing in four knockout rounds. These were the first round, quarterfinals, semi-finals, and final. Real Madrid won the first edition and has a record 13 titles in this competition.
In 1960, the event had an expansion to 32 teams. This necessitated adding an extra round. The other format of the sports league remained unchanged until 1992, when there was a major rebranding. The competition changed its name to UEFA Champions League. Also, a group stage replaced the initial round of the preceding tournament. This format is still in use up to date.
The coefficient of every member association in UEFA dictates the number of participating teams they will get in the tournament. UEFA draws these coefficients from the performance of the teams representing the association over the past five seasons in both tournaments.
Associations with higher coefficients get more qualifying slots. Consequently, the teams from these high-ranking associations play fewer qualification phases. The competition has seen 22 winners over the years. Chelsea FC is the most recent winner and defending champion.
For the lower-ranking teams, qualifications start in the summer. The teams play three phases and a knockout match to enter the group phase, which commences in September. The phase has eight groups, each with four teams. Every team in the group plays two games, home and away, against the same opponent. The best two teams proceed to the knockout phases. The third-ranking team drops to the lower-tier Europa League.