Billie Eilish will become Glastonbury's youngest ever solo headliner when she plays the Pyramid Stage on Friday.
The 20-year-old tops the bill just three years after her Glastonbury debut at a jam-packed Other Stage in 2019.
That year, her set had been upgraded from the much smaller John Peel tent after the phenomenal success of her breakout hit, Bad Guy.
Speaking from the stage, she lamented that she would never be able to experience the festival as a fan.
"This looks fun to go to," she said. "I would love to go to this… My God."
But the star's early evening set was plagued by technical issues that overshadowed the experience for her, if not the crowd.
"Thank you for not leaving. I know you could have," she said towards the end of her performance.
Friday's show should be less problematic, as Eilish has been fine-tuning her live show over months of intensive touring in the US and Europe.
The star is currently in the middle of a sold out, six-show run at London's O2 Arena, where she's been playing her second album, Happier Than Ever, almost in its entirety.
The Grammy-nominated record comments on the difficulties of her sudden and extreme fame, including its effects on her mental health and relationships.
On the opening track, Getting Older, she adopts a weary sigh as she sings: "Things I once enjoyed, just keep me employed now."
Eilish says the songs reflect on a period of depression that led to suicidal thoughts during the early stages of her career.
"I don't want to be too dark but I genuinely didn't think I'd make it to 17," she told CBS news in 2020.
The singer eventually sought help from her mother, Maggie Baird, who helped her access therapy. Making her second album during the pandemic also helped her combat the feelings of "joylessness" she'd experienced in her teens.
"All I can say now is, for anybody who isn't doing well, it will get better," she said. "Have hope. I did this with fame riding on my shoulders.
"Now I love what I do and I'm me again. The good me.
"And I love fame… I love the eyes on me."
That's been apparent at her recent UK shows, where she has been greeted with the sort of mania once reserved for the Beatles and Michael Jackson.
In London two weeks ago, she called one of her concerts to a halt after several fans passed out, overwhelmed at being in their idol's presence.
When she plays Glastonbury, the audience will be a mixture of those diehard fans and casual onlookers - but Eilish is guaranteed to leave an impression.
Despite a teenage dance injury, which affected the growth plate in her femur, she bounds across the stage with wild abandon - her legs taped up to avoid further damage.
"I love movement," she told the BBC in 2017. "I love moshing.
"I always head right for the front and dig in there and mosh really hard with all the guys. None of the girls want to mosh so I'm, like, the only girl getting punched in the face."
Eilish tops the bill on the first full day of music at Glastonbury, after performances from the likes of Sam Fender, Crowded House and Robert Plant & Alison Kraus.
Saturday night will see Paul McCartney headlining the Pyramid Stage - becoming the festival's oldest-ever headliner.
Diana Ross plays the legend slot on Sunday afternoon, with Pulitzer Prize-winning rapper Kendrick Lamar closing the festival that night.
Fans have endured travel chaos en route to the festival, with train strikes resulting in heavy traffic congestion on the approach to the site, at Worthy Farm in Somerset.
However, festivalgoers who did attempt to make it to Glastonbury by rail on Thursday were pleasantly surprised by the available train capacity.
They were rewarded with sets by Sasha, Skream, Bad Boy Chiller Crew and Four Tet as music started up on the festival's smaller, outlying stages.
Spice Girl Melanie C caused chaos with an early evening DJ set, that shut down the William's Green area.
Sporting a top with the legend, "Alexa, play Spice Girls", she played tracks by Dua Lipa, Megan Thee Stallion, Nirvana, Acraze and Rosalía, as well as dance remixes of Spice Up Your Life and Who Do You Think You Are?
She was followed by Glastonbury organiser Michael Eavis, who performed renditions of hits such as You Are Always On My Mind and Frank Sinatra's My Way with a six-piece band.
The 86-year-old was cheered as he left the stage with chants of "We love you Michael, we do".
Bastille also played a secret set, accompanied by the brass band Ol' Dirty Brasstards.
Around the site, there's a sense that fans are eager to get the festivities under way, after two years in which the festival was cancelled.
"We've been in prison for two years," one couple told BBC News. "We booked our tickets 991 days ago and here we are... So we are very excited."