Jamaica's Elaine Thompson-Herah made history with the first women's Olympic sprint "double-double" on Tuesday, as superstar gymnast Simone Biles stared down the dreaded "twisties" to bravely win bronze.
Thompson-Herah's blistering 200 metres win, following her brilliant 100m victory, made her the first woman to win both Olympic sprints twice in a row, evoking memories of her retired compatriot Usain Bolt.
It rounded off a stunning day on the track, when Norway's Karsten Warholm obliterated his own 400m hurdles world record and Athing Mu, 19, became the first American woman to win the 800m in 53 years.
Thompson-Herah's 21.53sec was the second fastest ever seen after Florence Griffith Joyner's world record of 21.34, set at the drug-tarnished 1988 Seoul Olympics.
As well as becoming the first woman to claim a 100m-200m double-double, the 29-year-old is the only female track and field athlete to win four individual Olympic golds.
"It really means a lot to me to be in that history book, because I've been through a lot and it tells my story," the Jamaican said.
Namibia's Christine Mboma, who was only running the 200m because she is barred from her preferred 400m for elevated testosterone levels, took silver in 21.81, while the USA's Gabby Thomas took bronze in 21.87.
Gymnast Biles had pulled out of her other finals as she battled a disorientating mental block, but she returned in medal-winning style to high excitement at the Ariake Gymnastics Centre.
The American four-time gold-medallist, widely considered the "GOAT" (Greatest Of All Time) put in a solid routine including a double backward somersault and double pike dismount, smiling broadly as she was congratulated by her teammates.
Biles was lying in the silver medal position until the final competitor, 16-year-old Chinese Guan Chenchen, stepped up and scored 14.633 points to take first place, pushing teammate Tang Xijing into silver.
"I was just happy to be able to perform regardless of the outcome," said Biles, who revealed her aunt died two days ago.
"I did it for me and I was proud of myself for being able to compete one more time."
China's double world champion Zou Jingyuan won the men's parallel bars and Japan's all-around winner Daiki Hashimoto, 19, completed a breakout Olympics with gold in the horizontal bar.
- Hurdles epic -
Earlier, the Olympic Stadium witnessed one of the great races when Warholm shattered his own world record by nearly 0.8sec in an epic 400m hurdles final.
The 25-year-old stormed over the line in 45.94 seconds, pushed hard down the home straight by USA rival Rai Benjamin, who took silver in 46.17 -- the second fastest in history.
"I dream about it like a maniac," Warholm said, adding: "I didn't touch one hurdle. I was even able to find another gear coming home, so 'wow'. It's just so big."
There was more drama in the women's long jump, when Germany's Malaika Mihambo snatched gold from former champion Brittney Reese with her last leap of the competition.
Mihambo, 27, was lying in the bronze medal position ahead of her final jump, but powered down the runway to register a season's best of 7.00 metres and Reese could not respond. Nigeria's Ese Brume took bronze.
"It was, I think, the most exciting women's long jump competition in history," said Mihambo.
Swedish world record-holder Armand Duplantis leapt 6.02m to take pole vault gold, and Poland's Anita Wlodarczyk won the women's hammer for the third straight Games with a heave of 78.48m.
In cycling, Germany won the women's team pursuit gold in a world-record time of 4:04.242, and the Netherlands won the team sprint -- their first men's track title since 1936.
Briton Jason Kenny's silver in the team sprint made him the first track cyclist to win eight Olympic medals, just minutes after his wife, Laura, won her fifth medal in the team pursuit.
Sena Irie became the first Japanese woman to win Olympic boxing gold, defeating Nesthy Petecio of the Philippines on unanimous points to take the featherweight title.
And France's Mickael Mawem led the men's combined qualifications in sport climbing, one of the events that is making its debut as the Olympics seeks to reach new audiences.