Coco Gauff used her greater experience to fight back from a set down against 16-year-old Russian Mirra Andreeva to reach the French Open fourth round.
American sixth seed Gauff, who is still only 19, remained calm and turned the match around to win 6-7 (5-7) 6-1 6-1.
Andreeva, who turned 16 in April, was perhaps fortunate not to be defaulted after angrily hitting a ball into fans.
Poland's Iga Swiatek, who beat Gauff in last year's final, also progressed with a 6-0 6-0 win over China's Wang Xinyu.
Swiatek, going for a third Roland Garros title, needed just 51 minutes to record her first 'double bagel' at a Grand Slam.
The world number one will face 2019 US Open winner Bianca Andreescu or Ukraine's Lesia Tsurenko in the last 16.
Gauff is also waiting to find out who she will play, with Slovakia's world number 100 Anna Karolina Schmiedlova and American qualifier Kayla Day in action later on Saturday.
Gauff wins battle of the teenagers
With Gauff bursting on to the scene as a 15-year-old at Wimbledon in 2019 still feeling fresh in the memory, it felt odd seeing her in the rare position of playing a younger opponent.
Andreeva was still only 15 when she started her stunning run to the Madrid Open quarter-finals in April, turning 16 during the tournament and attracting praise from seasoned professionals - including Britain's former world number one Andy Murray - in the process.
Gauff insisted "age would not be a factor" when the two teenagers, who have practised together recently, played competitively for the first time.
But it was the American's greater experience that shone through.
In front of an enthralled Court Suzanne Lenglen, packed with fans eager to see two players who could be around at the top for years to come, the pair demonstrated their talent in a dramatic first set full of stunning shot-making, intense long rallies but also fragility.
Gauff fell a set behind on the same court in her opening match against Spain's Rebekah Masarova, saying afterwards she told herself not to "freak out" despite having lost her previous 15 matches when falling behind.
Instead, it was Andreeva whose frustration spilled over.
The youngster received a code violation, as per Grand Slam rules, in the first-set tie-break when she thumped a ball into the crowd and it hit a spectator, although the world number 147 could have been defaulted if umpire Timo Janzen had deemed it more serious.
She regained her composure to take the first set, but was unable to maintain her level as Gauff fought back.
"Mirra is super young and has a big future," Gauff said.
"I remember I played here when I was 16 so she has a lot to look forward to. I'm sure you'll see a lot more matches between us."