Since its revamp in 1992 the Champions League has become one of the most prestigious and lucrative club tournaments in the world. It is also the most popular in terms of television audience. The competition is based on a group stage, which is followed by a knockout phase, with the final held at a neutral venue.
The group stage is a key point in the structure, and has had some significant changes over the years. In the beginning, a number of teams were invited to participate, and not all of them had to be champions. The first group stage saw a mixture of national champions and the top teams from each UEFA nation’s domestic league.
In the second group stage, a system of seeding and a draw was introduced. The groups were smaller, and clubs played each other twice. The winners of the group advanced to the round of sixteen, and the bottom twelve were eliminated. The clubs ranked ninth through twenty-fourth then competed in a knockout phase play-off, which determined the final eight clubs that would advance to the round of sixteen.
The knockout phase is now a series of two-legged matches, with the exception of the final, which is traditionally played in a single leg. The home advantage in the quarter-finals and semi-finals is determined by a draw, which largely reflects the teams’ rankings from the league phase. UEFA has made one significant change to this arrangement, however, with teams that are ranked 1-4 guaranteed home second legs in the quarter-finals and semifinals. This was done to strengthen the synergy between the league and knockout phases, and create more sporting incentive for teams in the latter.