The Champions League is a premier football event in Europe. The top teams of every top league in Europe are seeded to play in the Champions League every year. The competition starts with a preliminary stage that leads to the main competition. The main competition has a group stage of 4 teams in 8 groups. Then, the group winners and runner-ups compete in the knockout stage - round of 16, quarter-finals and semi-finals over two legs. Finally, the final is played by the semi-final winners in a one-leg fixture.