The Champions League showcases the highest level of play in world soccer, letting UEFA steer billions of euros (dollars) in prize money from global broadcasting and sponsorship deals to clubs who can afford to pay the best salaries and transfer fees. It also offers fans around the world a glimpse of footballing brilliance and the drama that makes the game so appealing.

It is no wonder that the tournament, which starts this week, has become a symbol of European football. In its illustrious history, the competition has seen countless ups and downs, and each era contributed to its rich legacy.

Real Madrid is the most successful club in the competition’s history with fifteen titles, followed by AC Milan with seven. Several other teams have won multiple championships over the years, including Manchester United, Barcelona, Bayern Munich, and Juventus.

In the simplest premise, the Champions League is a competition between the champions of each of Europe’s national leagues. It grew to include more than 30 clubs after UEFA doubled the field in 1960, adding an extra round of knockout play but keeping the rest of the format the same.

This season, the number of participating clubs has grown from 32 to 36. The new format will drop the group stage and replace it with a single standings league, in which each team plays eight games, four at home and four away. Teams will be seeded based on their UEFA coefficient ranking and will be drawn against other teams from the same pot in a double-round-robin format.