USA s Sha Carri Richardson set out on her bid for a world sprint double with the fastest time in the 200m heats of 22.16sec (AFP)
Richardson will have her work cut out to emulate Silke Gladisch, who achieved the feat in 1987, Katrin Krabbe (1991) and Shelly-Ann Fraser-Pryce (2013).
Gabby Thomas, who beat Richardson in the US trials, and Jamaica's defending champion Shericka Jackson, who is out for revenge after taking silver in the 100m, will be formidable rivals.
Richardson went through the motions and moved down a couple of gears 20m before the line to time 22.16sec, the fastest of the heats, with veteran Ivorian Marie Josee Ta Lou taking second spot.
Ta Lou, 34, finished fourth in the 100m final but hopes she can roll back the years and repeat at least her 200m silver medal from the 2017 worlds.
"I had a good mindset today," said Ta Lou.
"The 100m final on Monday was tough because I know what I'm capable of, but at the end of the day I'm grateful to be here, grateful to finish fourth, because last year I wasn't able to do anything.
"I always give 200 percent, but now it is up to 1000 percent. I want to produce a surprise in the 200m."
Jackson also had a gentle trot to win her heat in 22.51sec.
The 29-year-old Jamaican walked off without a bead of sweat on her face while second-placed Victoria Shanti Pereira jumped up and down having set a new Singapore national record of 22.57sec.
"I was not expecting to finish with a time like that," said Pereira.
"My goal for this season was to qualify for the Olympics.
"Now I have that, a national record and a personal best in my first race at the world championships."
Thomas, running in the outside lane, made light of that coming off the bend well in command and sauntered across the line in 22.26sec.
If there is to be a shock Julien Alfred could be the one to provide it, the 22-year-old from St Lucia who placed fifth in the 100m final, easing home in her heat in 22.31sec.
Britain's 2019 200m world champion Dina Asher-Smith gave herself a much-needed morale boost in winning her heat in 22.46sec after admitting that her eighth place in the 100m final was disappointing,