The women's 400m hurdles competition has gone through tectonic shifts in recent years, with a crop of fearless athletes challenging what is believed to be possible.
The 21-year-old phenom Sydney McClaughlin leads the one-lap hurdles revolution taking the baton from United States compatriot Dalilah Muhammad following her recent world-record run.
Muhammad, 10 years McClaughlin's senior, has been the standard-bearer over the last five years, winning the Rio 2016 gold medal and breaking the world record twice in 2019.
Add rising Dutch star Femke Bol into the mix, and you have the makings of a race for the ages.
Tokyo 2020 takes a look at these leading women and how they stack up against each other ahead of the Olympic showpiece.
The heir apparent
McClaughlin's rise through the world athletics ranks has been anything but surprising after she qualified for her first Olympic Games when she was just 16 years old.
Since her debut in Rio 2016, McClaughlin has been living up to her immense promise setting age-group records in the 400m hurdles, including world records at Under-18 (54.15) and U20 (53.60), before adding the senior global mark to her name at the US trials in June 2021.
While McClaughlin has set the track ablaze, she is still looking to translate her times into titles at a senior level.
The former world youth champion came painstakingly close to the podium's top step at the 2019 Doha World Championships, where she was pipped to the line by Muhammad with a world-record breaking effort.
McClaughlin crossed the line just 0.07 behind Muhammed, claiming a creditable second place just two months after her 20th birthday.
The prodigy turned the tables at this year's US Olympic trials in Eugene, where she usurped Muhammad of her throne and world record with a time of 51.90, becoming the first woman to dip below 52 seconds over the one-lap barriers.
"It's one of those moments that you dream about and think about when you're going to be able to put it together," McClaughlin told World Athletics.
"I knew, from the moment I woke up today, it was going to be a great day. Afterwards, there was a real 'I did it' moment, and I'm going to cherish this for the rest of my life.
"It was a really great competition, as always, and I knew it was going to be a fast race."
The reigning champion
Muhammad may have lost her vice-like grip on the 400m hurdles event, but the defeat to the young pretender may serve as extra motivation in her Olympic title defence in Tokyo 2020.
The 31-year-old Muhammad has been a constant force in the women's 400m hurdles since she was crowned world youth champion in Ostrava 2007.
She stepped onto the podium at the senior world championships for the first time in Moscow 2013 on debut before injury-plagued 2014 and 2015 seasons hindered her progress.
Muhammad turned in a dominant performance in her Olympic debut leading the race from start to finish, clocking 53.13 to claim victory by 0.42s.
Still, the world title evaded her at the 2017 London World Championships, where she finished second behind compatriot Kori Carter.
Muhammad confirmed her status as the 400m hurdles queen when she eclipsed Yuliya Pechonkina of Russia's world record from 2003, beating McClaughlin at the 2019 US championships with a time of 52.20.
The race served as a preview to the Doha World Championships, where she would further lower the global mark by 52.16 to finally get her hands on the world title beating McClaughlin by 0.07s.
The young pretender
Rising Dutch star Bol has emerged as the biggest threat to US women's dominance in the event at this year's showpiece.
The 21-year-old Bol has experienced a meteoric rise in 2021, setting 12 Dutch records – three in the 400m hurdles – raising her prospects as a medal contender in Tokyo 2020 Games.
She launched herself into fourth place on the world all-time list when she clocked a blistering 52.37 seconds at the Diamond League meeting in Stockholm at the beginning of July. The time is the second-fastest this year behind McClaughlin's world record, while she is also one of only four women to have dipped below 52.50 in 2021.
"We have such an amazing field," Bol told World Athletics.
"I mean, the world record for women and men was broken in one week for both – it's amazing to see the level of the 400m hurdles keep going up and that with my time, I am now second in the world this year, not even first. Of course, you want to be first, but when the level in your event is so high, I think that is the best."