Neymar and Mbappé have one particular advantage on the counter-attack - their speed on and off the ball.
Winning the ball from Liverpool's attack, PSG drove forward down the left flank with the Frenchman and Brazilian combining.
Mbappé, in masses of space on the left side of the area, drove into the box and knocked the ball across the face of goal for Cavani, who could only find the goalkeeper.
Luckily, Neymar was in the box and sprung for the rebound, finding the far corner of Alisson's goal with his left boot.