Serena Williams fought back from a set down and set a new Wimbledon women's record of 23 aces to keep alive her bid for a fifth singles title.
Williams, 30, had to dig deep to edge past China's Zheng Jie 6-7 (5-7) 6-2 9-7, while defending champion Petra Kvitova breezed into round four.
"I definitely felt like it was a gut check for me," said Williams.
"I never felt I would lose. I told myself to stay calm. I'm always strong mentally. That's not going anywhere."
The American, who set the previous aces record of 20 in the 2009 semi-final against Elena Dementieva, stumbled in the first-set tie-break.
But she romped through the second set before coming out on top in a nail-biting decider after two hours and 28 minutes on Centre Court.
"I thought in the third set, if I'm going to go out I want to go out with a bang," said Williams, who served three times to stay in the match, winning each game to love.
Williams, the sixth seed, will next play Kazakh wildcard Yaroslava Shvedova, who made history by achieving the first 'golden set' in Grand Slams against Sara Errani.
French Open finalist Errani failed to win a single point during a 15-minute first set, in which Shvedova won 24 consecutive points, and eventually fell 6-0 6-4 to the world number 65.
"I had no idea," said Shvedova of her remarkable run of points.
"I was just playing every point and every game. I didn't feel like it was every game was 40-0.
"I was so focused in such a zone. I remember like first or second ball of the second set she won. All the people start to like clap and scream. I was like, 'What's going on?'"
"She was impossible to play against," Errani said. "I don't even feel like I played a disastrous match. She was hitting winners from every part of the court."
Czech fourth seed Kvitova eased through with a 6-1 6-0 victory over American Varvara Lepchenko.
Kvitova, who has lost just 13 games in three matches, hit 15 winners and forced her opponent into 38 errors.
"I feel better every match that I'm playing here," said 22-year-old Kvitova, who has yet to drop a set in the tournament.
The Czech said she would play "aggressively" against her next opponent Francesca Schiavone, who beat Klara Zakopalova 6-0 6-4.
"Francesca can play very well on the grass with a good slice from the backhand," she said. "We played twice already this year on clay and hard court so we're just missing the grass, so it's time for this.
"I think she can play very well, she has a good volley, so I think she will play aggressively going to the net."
Ana Ivanovic, the 14th seed, beat Julia Goerges of Germany 3-6 6-3 6-4 and will meet second seed Victoria Azarenka.
Australian Open champion Azarenka, last year's semi-finalist, beat Slovakia's Jana Cepelova 6-3 6-3, despite only securing five of 12 break points.
Austria's Tamira Paszek, who defeated former world number one Caroline Wozniacki in the first round, also progressed with a 2-6 7-6 (7-4) 7-5 win over Yanina Wickmayer of Belgium.
She will next play 21st seed Roberta Vinci after the Italian secured a 7-6 (7-4) 7-6 (7-3) victory over Croatia's Mirjana Lucic.