Liverpool have reached their third Champions League final in five seasons after beating Villarreal 5-2 on aggregate.
Jurgen Klopp's side blew a two-goal first-leg lead in Castellon, as goals from Boulaye Dia and Francis Coquelin threatened a historic upset.
After Fabinho's close-range finish, Luis Diaz's half-time introduction turned the tide for Liverpool.
Sadio Mane pounced on Geronimo Rulli's error to score a third goal, before Etienne Capoue was sent off for a second booking.
Liverpool's 2022 quadruple dreams were in jeopardy in Castellon, so Klopp turned to his bench on a big European night.
To beat Inter Milan in the last 16, Diaz and Firmino came on late, and he did so again tonight.
Diaz's immediate impact since signing in January has quickly moved him up the pecking order.
His directness and pace unsettled Villarreal's defence after the break, allowing new spaces to open up.