Switzerland completed a remarkable comeback in a penalty shoot-out after Tuesday's (AEST) dramatic 3-3 draw in Bucharest, where Yann Sommer emerged the hero after saving Kylian Mbappe's spot-kick.
Having opened the scoring and seen Ricardo Rodriguez's penalty saved by Hugo Lloris early in the second half, Switzerland found itself 3-1 behind with 15 minutes of regulation time remaining.
But Haris Seferovic netted his second of the game in the 81st minute before Mario Gavranovic's last-gasp strike forced extra-time after cancelling out Karim Benzema's brace and Paul Pogba's stunner.
Sommer then stepped up with the decisive save in the shoot-out after extra time to send Switzerland through to the quarter-finals at a major tournament for the first time since the 1954 World Cup.
"It is f****** amazing man," Switzerland captain and man of the match Xhaka – who refused to rule out a move to Jose Mourinho's Roma from Arsenal – said.
"We lose two goals and then we go up. Then the penalty we missed broke us a bit. We showed a beautiful character. It's a hell of a team.
"We showed a lot of character, I don't even know what to say. In 10 minutes, we go back to 3-3. The last 30 minutes we were better, we wanted to finish and win before the penalty shoot-out. In the end, we are qualified. We are writing the history of our national team."
It was the first time in Switzerland's history that they had won a penalty shoot-out at a European Championship or World Cup, thanks to Sommer's save.
As Switzerland look ahead to Friday's showdown with Spain in St Petersburg, Sommer said: "What a match! What an evening of football.
"It was our chance to finally go through the round of 16, because we never made it before. It's incredible, we played with heart and with character. It’s amazing.
"It was a really difficult situation for us after the penalty miss. I'm really proud of the team, how they came back. We always believed. Even before the game we said no matter what happens in the game, it doesn't matter if we're down, or if things are going well; we play until the end, we never give up.
"It's always 'anything is possible'. We believe. We said before the game that we are a small country, but we have a lot of quality and a lot of experience and we showed it tonight."