Alex Telles stepped up to the penalty spot to send Porto into the Champions League quarter-finals with a win over Roma in a game dominated by VAR.
Tiquinho Soares put the home side ahead midway through the first half with a strike that was eventually awarded after a VAR review.
Daniele De Rossi netted from the penalty spot 10 minutes later to level the tie on the night.
But Moussa Marega put the Portuguese side back in front seven minutes after the interval.
As the game headed to extra-time, Telles struck from the spot to edge a dramatic last-16 second leg.
Eusebio Di Francesco had made a number of controversial calls in the wake of the 3-0 defeat to fierce rivals Lazio, with Alessandro Florenzi, Lorenzo Pellegrini and Stephan El Shaarawy all starting on the bench as Roma set up with an unfamiliar 3-4-3 setup.
And it appeared to have little effect as Porto dominated the early stages, with both Jesus Corona and Tiquinho Soares going close.
The opener arrived when Kostas Manolas was robbed of possession and Corona brought the ball forward. He waited for the overlap from Moussa Marega, who squared to Tiquinho to slot home.
After a brief VAR check for offside, referee Cuneyt Cakir awarded the goal that gave Porto the lead.
But then a clumsy error from Eder Militao would give Roma the chance to get level again. Diego Perotti cut in from the left and the young Brazilian hauled down the playmaker, leaving the referee with no option to point to the spot.
Up stepped De Rossi, who stuttered before sending Iker Casillas the wrong way with a well-struck penalty into the bottom corner.
Seven minutes after the interval, Porto were back in front. Corona produced a stunning cross which left the Roma backline rooted to the spot and at the back post was Marega to touch it past Olsen.
Edin Dzeko and Pepe then came to blows off the ball and the latter was perhaps fortunate not to see a red card after appearing to aim a headbutt at the Bosnian.
Both sides had chances to win it in the second half as the game grew more tense by the minute.
In the second half of extra-time, Dzeko had two chances to win it, first blasting over the bar and then, a minute later, lifted his shot over Casillas only for Pepe to heroically clear off the line.
And that was vital because with five minutes left, VAR intervened again to award Porto a dramatic late penalty. Florenzi, on as a substitute, pulled back Fernando in the box and referee Cakir pointed to the spot.
Up stepped Telles, in the 115th minute, with the pressure on his shoulders. But he looked calm and collected to send Casillas the wrong way and send Porto into the quarter-finals.
