Georginio Wijnaldum's quick-fire double gave Liverpool a huge chance of reaching the Champions League final.
The Dutchman only came on as a substitute at half time after an injury to full-back Andy Robertson, which saw James Milner deputise in defence at left-back.
And the 27-year-old showed perhaps why he should have started this game, arriving late in the box to meet Trent Alexander-Arnold's deflected cross.
Despite pressure from Ivan Rakitic, the midfielder hit a powerful effort from close range and it squirmed under Marc-Andre ter Stegen.
Liverpool felt that Barcelona were there for the taking and that would soon prove to be the case as Wijnaldum got his second just two minutes later.
Xherdan Shaqiri crossed from the left and with three Barcelona defenders present at the near post, Wijnaldum rose high above them to nod past the helpless Ter Stegen to send the Anfield crowd into pandemonium.
That goal levelled the tie on aggregate and had the Reds dreaming of a third Champions League final in Madrid on June 3.
