The Dutch sprinter Dafne Schippers completed her transformation from heptathlete to world champion sprinter when she ran the fourth fastest 200 metres of all time to win by a nose at the Bird's Nest in Beijing.
The 23-year-old European champion clocked 21.63 seconds to beat Jamaica's Elaine Thompson by three-hundredths of a second and add gold to the silver medal she won in the 100 metres behind Jamiaca's Shelly-Ann Fraser-Pryce.
Only Americans Florence Griffith-Joyner, the world record holder, and Marion Jones, who was later banned for doping, have run faster.
"I can't believe it," said Schippers, who only switched her focus to the sprints full time this year.
"What a race! What a tournament for me! I think they'll be going crazy in the Netherlands at the moment."
Twice Olympic champion Veronica Campbell-Brown took bronze (21.97) in a race which featured two of the five fastest 200 metres of all time and six of the seven fastest of 2015.
The American Aries Merritt has won bronze in the 110 metre hurdles even though the Olympic champion will undergo a kidney transplant on Tuesday.
The world record holder finished third behind Russian Sergey Shubenkov and the delighted 30-year-old explained why his sister was not cheering him on at the Bird's Nest.
"It almost means more to me than my Olympic gold, the state I'm in, the training I've done, it's been very difficult. The struggle is real," Merritt said.
"My sister's going to give me one of her kidneys. That's why she didn't come to Beijing, she did not want to endanger the transplant."
Jamaica's Danielle Williams had her sister Shermaine alongside her when she enjoyed the finest moment of her career with a shock win in the women's 100 metres hurdles.
It was the first time siblings had competed in a world championship final and it was the younger sister who stormed to victory in a personal best 12.57 seconds ahead of Germany's Cindy Roleder and Alina Talay of Belarus.
Williams did benefit from three of the American favourites succumbing to the pressure, two going out in the semi-finals and the other clipping her first hurdle, but nothing was going to deny her family their delight.
"It was so special that we were together in this final," said Danielle, whose sister finished seventh.
"There will be a big celebration for sure, my family is shouting, celebrating -- they look even happier than I am."
The American Tianna Bartoletta rolled back the years in the women's long jump, snatching a second world title with a leap of 7.14 metre a decade after she won her first under her maiden name Madison.
Her best jump was her last and Britain's Shara Proctor, who had led the competition after breaking her own national record with a 7.07 metre jump in the third round, fouled with her final effort.
China's Liu Hong and Lu Xiuzhi looked a little like siblings as they matched each other stride-for-stride until the last few steps of the 20 Kilometre walk.
Liu led Lu over the line in a time of one hour 27 minutes and 45 seconds for the first gold of the day, to the delight of the crowd basking in the morning sunshine.
"I felt a lot of pressure. China had not won a gold medal and everybody was waiting for it," Liu said.
Russian walker Alexander Yargunkin will not compete in the men's 50 kilometre walk on Saturday after being suspended while the Russian anti-doping agency (RUSADA) investigates media reports he tested positive for blood-boosting agent Erythropoietin.
It will be the first time no Russian walkers will take part in a world championships.