No-one will be taking Wales lightly any more after they produced a stirring performance, complete with a Gareth Bale stunner to open their campaign with a win.
Bale, a potential star of the tournament, made an instant impact on the game with a brilliant free kick, but Hal Robson-Kanu made the most decisive contribution with a scuffed effort to spark wild celebrations and put a bit of pressure on England ahead of next week.
Here's what happened:
The game in one line
It was about more than one man or one goal. It was a big day for Wales after a long absence from international tournaments, and it was a day to celebrate.
1. Ben Davies' wonder-save (3):
With not even three minutes on the clock, Marek Hamsik waltzed through the Welsh defence and looked certain to score, only for Ben Davies to come from nowhere and clear the ball off the line. The floodgates could have opened early on but Wales took heart and went up the other end minutes later to score.
2. Gareth Bale's stunning opener (10):
They were under pressure early on, but Bale announced himself to the tournament in the best possible way. He stepped up to a 30-yard free-kick and smashed it into the back of the net to send everyone wild.
3. Hal Robson-Kanu's dramatic winner (81):
It looked like it was heading towards a draw until a fine ball from Joe Ledley found Aaron Ramsey, and the ball eventually found Robson-Kanu who scuffed the ball in to claim a huge win.
Aaron Ramsey's hair. He's obviously trying to revive the spirit of Gazza and 1996, but we're not a fan. He wasn't the only one to be fair, Slovakia were boasting some fairly shocking cuts of their own.
Who played badly?
Martin Skrtel. A poor game for such an experienced defender. He should have seen red and conceded a penalty for a poor tackle on Jonny Williams, before another poor tackle on Ben Davies later on.
Was it the right result?
Would you argue with it? An emotional performance from an underrated side. It's hard to say they didn't deserve it and they certainly boasted the best players on the pitch.
Bale made a big play before the game about the Wales motto being #TogetherStronger, and the team unity was for all to see as their star man ran to celebrate his stunning opener with the rest of the squad.
Best quote (/fan of the day)
Classic Savage. Sometimes you get the feeling he dives into statements the same way he used to tackle, but you can't argue with Robbie in this case. Martin Skrtel should probably have seen red.
In the stands
With it being Wales' first appearance at a major international tournament since 1958, it was always going to be an emotional day for players and fans. The national anthem brought goosebumps, and there was a touching tribute to the late Gary Speed from the travelling fans.
There is no doubt he is Wales' superstar and main man. He dragged them through qualifying and thrived on the responsibility here. Though well-shackled at times, he stepped up when it mattered to open the scoring and produced moments of quality throughout that will give England something to think about next week.