Rising American sprint star Gabby Thomas set the fastest time in the world this year in the women's 200m at the US trials in Oregon on Thursday as Allyson Felix squeezed into the semi-finals.
Harvard graduate Thomas, who is studying to be an epidemiologist, became the first woman to duck under the 22-second barrier this year, powering home in 21.98sec at Hayward Field.
Thomas, who had already booked her place at the Tokyo Olympics after a fifth-place finish in the 100m on Saturday, warned she still had plenty left in the tank.
"I wasn't expecting the time but I'm happy with it," Thomas said. "It's surreal. I know I've been working really hard and have a great team around me.
"I was surprised. I slowed down at the end. I think I have more left."
Thomas's time marked her out as the early favorite for the 200m gold in Eugene, a task that has been made simpler after 100m champion Sha'Carri Richardson scratched from the event this week.
But while Thomas impressed, US track and field's veteran superstar Felix was less convincing.
Felix, the 2012 Olympic 200m champion, had also already punched her ticket to Tokyo with a second-place finish in the 400m, said she had planned to "have fun" with the 200m this week.
The six-time Olympic gold medallist placed third in her heat in a time of 22.56sec but that was good enough to qualify her for Friday's semi-finals.
Felix, who will be competing in her fifth straight Olympics at Tokyo, is expected to opt for the 400m at the Games, with the schedule not realistically allowing for a 400m-200m double.
- Mighty Mu -
While Thomas shone in the 200m, another emerging track prodigy, Athing Mu, impressed in the 800m heats.
The 19-year-old college student from New Jersey, who on Wednesday announced she is turning professional after signing with Nike, impressed with a composed performance in her opening heat, winning in 2min 0.69sec.
Mu, who has smashed a series of junior and collegiate records this year, is bidding to become the first American woman to win an Olympic 800m gold since Madeline Manning's victory at the 1968 Mexico City games.
While Mu has been hailed as a potential Olympic star, the youngster said she is not letting plaudits go to her head.
"I take everything that people say about me lightly," said Mu, whose parents settled in the United States after fleeing civil war in Sudan in 2001.
"I'm just coming out here to run my races and have fun," Mu said.
"It's awesome people wanting to take pictures with me, but I'm just doing the same thing I've always done."
In the only track final of Thursday, Emma Coburn secured her third straight Olympic spot with a masterful victory in the 3,000m steeplechase.
The 30-year-old 2017 world champion looked comfortable throughout a race held in sultry conditions as a heatwave-baked southern Oregon.
Coburn pulled away with Courtney Frerichs with two laps to go and then kicked hard on the last lap to win in 9min 9.41sec.
It means Coburn will have another opportunity to land an Olympic medal after a bronze at the 2016 Rio de Janeiro Games.