Dina Asher-Smith's rivals sent out an Olympic warning in Tokyo as the Team GB star qualified for the 100 metres semi-finals.
The world 200m champion clocked 11.07 seconds in heat one on Friday, easing down to finish behind the United States' Teahna Daniels.
But defending champion Elaine Thompson-Herah made a statement with a run of 10.82 seconds – initially the fastest opening round in the event's history at the Olympics.
The Ivory Coast's Marie-Josee Ta Lou then ran 10.78 seconds and favourite Shelly-Ann Fraser-Pryce, the double 100m champion, clocked 10.84 on the first morning of the athletics at the Olympic Stadium.
No British female has won an individual Olympic sprint medal since Dorothy Hyman claimed 100m silver and 200m bronze in 1960.
Asher-Smith, who qualified joint 11th fastest for Saturday's semi-finals, said: "I do have another level – of course I do, it's an Olympics.
"To be honest today was just about making it through to the next round safely at the same time as knowing I've got another level to give tomorrow, so I am really happy.
"You are trying to go and perform and do well. As an athlete you love a full stadium, you love spectators but at the same time it is what it is and you've still got the job to do."
Team GB's Daryll Neita ran a personal best of 10.96 seconds to qualify and Asha Philip also progressed.
In the 800m, Jemma Reekie won her heat in one minute 59.97secs to reach Saturday's semi-finals.
"That was good, I'm glad to get that done. It wasn't quite as I would have liked, I didn't quite do what I wanted but I'm through and that's the main thing," she said.
"It was a little bit messy and I was a little bit all over the place but that's job done now and I can aim at tomorrow."
Keely Hodgkinson finished second in her heat in two minutes 01.59 seconds to qualify, with the British champion wearing shoes with slogans written on by family and friends.
She said: "It's definitely been different to what I'm used to, even with the European seniors. It's just bigger, isn't it?
"Everyone watches the Olympics, it's big for everyone, so there's definitely been a lot more attention around it, but I'm enjoying it and I'm taking it all in, and hopefully I've got a couple more Olympics in me.
"I just wanted to make sure I wasn't too slow to give other people a chance. I'm just happy I got the job done. I want to be in that final just as much as everyone else."
Alex Bell finished fourth but reached the semi-finals as one of the next six fastest outside the automatic qualifiers.
Tom Gale qualified for the high jump final after clearing a season's best of 2.28m but Lawrence Okoye failed to make the discus final after recording three no throws on his return to the sport having tried to crack the NFL in 2013.
Zak Seddon did not progress from his steeplechase heat to cap a nightmare Games.
He was one of six Team GB track and field athletes and four staff having to self‑isolate, despite repeatedly testing negative, after being pinged as close contacts of an infected passenger on their flight to Tokyo
He said: "It's not been great and mentally it's been hard here, there and everywhere. In this day and age that's what sport is and some athletes are going to get easier rides than others but you have to deal with it.
"You don't get points on the finish line for having different build-ups, you know? The numbers on the scoreboard are what counts."
