As the Champions League final approaches, there's always the chance we could see the match head into extra time.
So how exactly does extra time work?
Teams can draw during the Champions League group stage but not in the knockout rounds.
During a two-legged round, the match can end in a draw in the first leg. In the second leg, ties are given to the team with the most away goals during both legs.
The match heads to extra time if both teams have the same number of away goals after two legs of play.
Extra time consists of two 15-minute periods, no matter what—there's no golden goal rule. The away goals rule continues to apply here, so if the away team scores in an extra time, the home team must score twice to break the deadlock.
If the two teams remain level through all that, then the match goes to penalty kicks. Penalties are best of five, with teams taking turns until one team mathematically cannot win. If teams are level through five penalties, they keep going until the tie is broken (on the same turn, someone scores and someone else does not).
Back in March, IFAB announced some changes to club competition regulations starting in the 2018-19 season. These changes will go into effect for the Champions League, Europa League and Super Cup and include a rule on extra time.
Starting next season, a fourth substitute listed on the match sheet can participate in extra time during knockout matches.