Seventeen-year-old Victoria Duval stunned former champion Sam Stosur to reach the second round of the US Open under the lights at Flushing Meadows.
The American made her debut last year, losing to Kim Clijsters in the first round, and she came through qualifying to reach the main draw this time.
Stosur edged the first set and it looked like Duval would head off court a plucky loser when the Australian, who beat Serena Williams in the final two years ago, went a break up in the second.
But Stosur's confidence has never been the most robust and Duval fought back to take the second set.
The crowd on Louis Armstrong realised they could be watching something special and roared their girl on as she broke 11th seed Stosur again to forge ahead in the decider.
Finishing the match was a nervy business, Duval seeing a match point come and go on the Stosur serve and then being forced to save break points when she served for it.
But on her third chance she put away a volley and leapt for joy at her 5-7 6-4 6-4 victory.
America appears to have a golden generation of young female players, but few of them have pulled off a result as spectacular as this.
Petra Kvitova went the distance again as she moved into the second round with victory over Japan's Misaki Doi on Arthur Ashe.
The seventh seed plays a remarkable number of three-setters and a second-set lapse cost her again here, although she recovered well in the decider to defeat Doi 6-2 3-6 6-1.
Kvitova, the 2011 Wimbledon champion, has been consistent only in her inconsistency this season and this win was a fifth three-setter out of her last six victories.
The Czech next meets Serbian Bojana Jovanovski, who put out Germany's Andrea Petkovic 6-2 6-4.
Ana Ivanovic was the first winner of the day, the 13th seed thrashing Anna Tatishvili 6-2 6-0 in just 58 minutes.
Ivanovic split from British coach Nigel Sears after Wimbledon and is now working with Serbian pair Nemanja Kontic and Zlatko Novkovic, and Sven Groeneveld through her sponsors, adidas.
The former world number one had enjoyed good preparation for the US Open until a first-round defeat by Alize Cornet in Cincinnati.
Ivanovic said: "I've been playing really well and I had a few tough losses. It's obviously hard, more so emotionally than anything else. I'm very confident with my game.
"I know I did a very good preparation. I have a new team with me. Obviously it takes time to get comfortable, to get things to work smoothly. I'm very happy at the way everything is."
Sixth seed Caroline Wozniacki won the final five games of the match to beat Duan Ying-ying 6-2 7-5.
Wozniacki's boyfriend Rory McIlroy watched on as the Dane was pushed hard by big-hitting Duan but she dug in, saving seven of 10 break points she faced.
Wozniacki said: "I felt good out there. I feel like the game is where I want it to be. I love the hard courts, and playing on Arthur Ashe as my first match is great. I was really excited."
The 23-year-old has not reached a grand slam quarter-final since the Australian Open last year, but her section of the draw is very open and she has a very good chance of going at least that far.
The highest seed in the quarter is fourth seed Sara Errani, who has not been in great form but could not have done better as she thrashed Olivia Rogowska 6-0 6-0.
The second round begins on Wednesday, with both Williams sisters in action.
World number one Serena meets Galina Voskoboeva on Arthur Ashe while Venus takes on Zheng Jie of China on Louis Armstrong.