Coco Gauff defeated Venus Williams 7-6 (7-5), 6-3 to progress to the second round of the Australian Open for the first time.
The 15-year-old fought hard to see off the former two-time Australian Open champion. Gauff edged the opening set in the tie break after Williams broke back to level at 5-5.
And the second was a more straightforward set for the teenager on the Margaret Court Arena as she capitalised on Venus' unforced errors before taking it 6-3 with some impressive tennis.
"She played well, like I said," Williams told reporters. "Just played very focused and put a lot of balls in the court. That's what you have to do. She'll play well the rest of the event.
"She clearly wants it, works very hard, is extremely mature for her age. I think the sky's the limit for her."
Gauff shone on her Australian Open debut on Monday as she knocked Williams out of the first round in a repeat of her stunning victory over the seven-times Grand Slam champion in the Wimbledon opener last year.
The 15-year-old American sensation, 24 years Williams' junior, eased to the win in the clash of generations at Margaret Court Arena, Gauff's first main draw appearance as a direct qualifier at a Grand Slam.
After sealing the first set tie-break when Williams struck an overhead smash into the net, Gauff broke her compatriot twice in the second before serving out the match to love.
Gauff will face Romanian Sorana Cirstea, who earlier beat Barbora Strycova 6-2 7-6(5), for a place in the third round.
"That was really difficult," Gauff said on Eurosport. "She played really well and, I mean, I was really nervous for today's match. I was a bit shocked, I'm sure everybody was shocked, when they saw the draw come out but I'm glad that I was able to get through it.
"I'm feeling great. I really like this court and I really like this crowd so thank you guys."