Judoka Wojdan Shaherkani became the first woman from Saudi Arabia to compete at the Olympics while Teddy Riner and home favourite Karina Bryant lit up the ExCel Arena on Friday.
Shaherkani, 16, walked onto the judo mat and bowed to her opponent Melissa Mojica of Puerto Rico before grippng up to make history.
But her debut lasted just 82 seconds before she was thrown for the maximum ippon.
She broke down in tears in her father's arms -- himself a referee at the competition -- as the crowd gave her a standing ovation.
"I'm proud, I'm happy and I want to continue in judo. I want to thank the fans for their support," said Shaherkani after it was all over.
"I was disturbed and afraid at the beginning, it was my first time in a big competition and there was a lot of pressure because of the hijab issue."
Shaherkani's headwear almost cost her this opportunity after International Judo Federation president Marius Vizer said she wouldn't be allowed to compete in a hijab.
In the end a deal was struck between judo officials and Saudi authorities and she appeared in a black, swimming cap.
Once the euphoria of her moment had died down, the business of chasing the last two judo gold medals on offer at these Games took centre stage.
And the favourites looked in ominous shape.
Five-time world champion Riner is looking to make up for the disappointment of missing out on gold in Beijing, where he took bronze.
And he gave every indication that he will take some stopping.
He had to content himself with a victory on penalties over 170kg Pole Janusz Wojnarowicz.
Riner struggled similarly against Tunisian Faicel Jaballah until he struck with a picture-perfect uchi-mata (inner thigh throw), 11 seconds form the end.
And in the quarter-final he used brute strength to turn Cuba's Oscar Brayson over onto his back to pin him down.
He will face South Korean Kim Sung-Min in the semi-finals.
Kim beat Ihar Makarau of Belarus in the quarters. Until then Makarau had been wreaking havoc, beating fourth seed Islam El Shahaby of Egypt and then Japan's Daiki Kamikawa.
That loss ensured Japan's men will finish an Olympic judo competition without a gold medal for the first time ever.
It also meant the team overall cannot top the judo medals table, something that has not happened since the 1988 Olympics in Seoul, when they came third behind the hosts and Poland.
On the other side of the draw, second seed Andreas Toelzer made steady progress to the semi-finals where he will face former three-time world champion Alexander Mikhaylin of Russia.
The 32-year-old first won the world title in 2001, the same year as his first European crown and earlier this year he ended a five-year major title drought by snatching his sixth European crown.
In the women's division, reigning champion Tong Wen of China was impressive.
The seven-time world champion despatched all three of her opponents in double-quick time, the last with a brutal armlock.
She will meet Cuba's Idalys Ortiz in the last four.
On the other side Japan's second seed Maki Sugimoto was equally impressive, throwing both her opponents for ippon.
She will face home hope Karina Bryant in the semi-finals after the Briton turned around a losing position into a victory 12 seconds from the end of her clash with Kazakhstan's Gulzhan Issanova with an uchi-mata.