The UEFA Champions League is UEFA's elite club competition with top clubs across the continent playing for the right to be crowned European champions.
The tournament, then called the European Cup, began in 1955/56 with 16 sides taking part. It changed into the Champions League in 1992/93 and has expanded over the years with a total of 78 clubs entering in 2015/16.
Qualifying begins in the summer with three rounds and then a play-off taking place before 32 teams begin the group stage starting in September.
The group stage involves eight groups of four teams, with each club playing everyone else in that group home and away. The top two sides in each group move on to the round of 16 and the start of the knockout phase, while the third-placed team drops into the UEFA Europa League.
The round of 16, quarter-finals and semi-finals are played over two legs, home and away, while the final is hosted by a stadium which is selected almost two years in advance.
There have been three Premier League winners of the UEFA Champions League since it was formed, Manchester United (twice; in 1998/99 and 2007/08), Liverpool (2004/05) and Chelsea (2011/12).
Those four wins have produced plenty of drama. United staged an astonishing comeback with two goals in two stoppage-time minutes to defeat Bayern Munich 2-1 in 1999 while in 2005, Liverpool fought back from 3-0 down at half-time against AC Milan to force extra-time before winning the contest on penalties, the final being known as the Miracle of Istanbul.
United then beat Chelsea on penalties in 2008 in the first European Cup final to be played between two English teams but the Blues became the first London side to win the Champions League trophy four years later when they defeated Bayern Munich on penalties in Munich.
England have won 12 European Cup/Champions League titles in total with Liverpool leading the way with five triumphs. Man Utd have three, Nottingham Forest won it twice in 1978/79 and 1979/80, while Aston Villa and Chelsea have won it once.
The Premier League representatives in the 2017/18 Champions League will be champions Chelsea, Tottenham Hotspur, Manchester City and UEFA Europa League winners Manchester United. Liverpool, who finished fourth in the PL table, will compete in a qualifying play-off.
For more information on the UEFA Champions League, click here.