Hayden Panettiere speaks out on first intimate scene at 13 with '20 year old something guy'

Hayden Panettiere has revealed another wild story from her years growing up in Hollywood.

The Heroes actor has just released her memoir, This Is Me: A Reckoning, last week, which saw the former child star reflect on what it was like to be in the public eye from such a young age.

Panettiere has been acting since she was just 11-months-old, with the 36-year-old starring in franchises such as Scream, Bring It On and a leading role in musical drama Nashville.

However, the fame brought plenty of shocking moments, with Panettiere recalling uncomfortable moments with an older man, having a 'very famous' actor expose their testicles to her at the age of 19 and even alleging that she'd been 'groomed' during her early days in Hollywood.

Hayden Panettiere revealed her first make-out session happened while filming a movie (Raymond Hall/GC Images)

In her latest revelation, Panettiere told Entertainment Weekly that she had her 'first makeout' while filming Raising Helen at the age of 13.

"The first makeout ever in my life was on Raising Helen," she explained.

"My mom [was] watching me with a 20-something-year-old guy while I was 13."

While Panettiere did not name the actor with whom she shared the kiss, her character Audrey shares an on-screen romance with Michael Esparza, who was 20-years-old at the time of filming.

"I was shocked that he used his tongue! I couldn't believe it, and I didn't want to make a big deal out of it," she added.

"I was like, 'Oh, that's how it's done. Got it.'"

Panettiere had been 13-years-old at the time filming took place, with the actor revealing that she finds it strange to think back at how young she was.

"Can you believe I was 13 in that movie? At certain points, they had me dressed up like you would've thought [I was way older]," she recalled.

13-year-old Hayden Panettiere in Raising Helen (RJ Capak/WireImage)

"I look back at pictures, people tell me how young I look now, but it's crazy because when I was 13, I almost looked like I was a teenager — the tummy out, the smokey eyes."

Life milestones aside, the actor added that she had a lot of 'great memories' from working on the movie and praised the film's late director Garry Marshall as an 'incredible person to work with'.

Elsewhere in the book, Panettiere addressed her relationship with co-star Milo Ventimiglia, recalling the scrutiny over their 12-year age gap.

The couple dated for two years after Panettiere turned 18, with the actor explaining that the press scrutiny around their ages had been 'relentless'.

"The press scrutiny around our age difference had been relentless," she said, noting that it was particularly difficult for Ventimiglia, who was a private person.