Barcelona came twice from behind Inter Milan to take a draw in a thriller of six goals to maintain their Champions League semi -final.
Inter surprised the hosts after just 30 seconds when Marcus Thuram entered the low cross of Denzel Dumfries with a daring Backheel film to score the fastest goal in a last four competition in the history of the competition.
Dutch full-back Dumfries doubled the visitors' lead with a beautiful overhead kick 20 minutes later and it seemed that Barca had a mountain to climb.
But Lamine Yamal encouraged the magic to transform the game.
He hit a wonderful answer from the 24th minute while he drove in and hit several defenders before he let go of a left-hand foot finish that kissed the pole before landing in the net.
Yamal stood the core of everything Barca did and hit the woodwork twice, but marked his 100th appearance for the club with a 22nd goal to add to his 33 assists at the age of only 17.
Ferran Torres closed a fascinating first half with a 38th minute equalizer for the hosts, who stuck at home after Raphinha Pedri's Crossfield Ball ended.
But the impressive Dumfries scored his second of the night in the 63rd minute to restore the lead of Inter when he rose the highest around the corner of Hakan Calhanoglu.
But Barca reacted again in style and rode only two minutes later when a stinging of 25 meters from Raphinha was clattering the bar, down and bounced in the net, via a touch off inter-goalkeeper Yann Sommer's back.
The breathless affair leaves the draw on the balance with the second stage on Tuesday in the San Siro in Milan.
Line-ups
Barcelona XI: SZCZÄ™sny; Koundé, CubarsÃ, Iñigo MartÃnez, Gerard MartÃn; De Jong, Pedri; Yamal, Olmo, Raphinha; Ferran Torres
Subs: Iñaki Peña (GK), Astralaga (GK), Ronald Araújo, Gavi, Fati, Torre, Christensen, FermÃn López, Pau Victor, Eric GarcÃa, Fort
Inter XI: Som; Bisseck, Acerbi, Bastoni; Dumfries, ÇalhanoÄŸlu, Mkhitaryan, Barella, Dimarco; Lautaro MartÃnez, Thuram
Subs: Di Gennaro (GK), J. MartÃnez (GK), De Vrij, ZieliÅ„ski, Arnautović, Frattesi, Asllani, Augusto, Darmian, Re Cecconi, Zalewski, Taremi