A little over half an hour has elapsed in the Basque Country when the hosts took a shock lead against the European champions.
Whilst not the prettiest of goals, it was enough to raise the spirits of a delighted home crowd.
Markel Susaeta picked out the underlapping run of Oscar de Marcos down the right, with the utility man drawing Thibaut Coutois and crossing low into the middle.
The ball fell to Iñaki Williams and whilst he was unable to turn the ball home with conviction, the ball dropped perfectly for Muniain to sneak in ahead of Dani Carvajal and finish the job from barely a yard.
September 15, 2018
Bilbao thought they had struck the jackpot just minutes later as Raul Garcia side-footed home a free-kick from deep, but that goal was rightly chalked off for offside against the playmaker.