Katherine Heigl felt nervous playing a college-aged student in 'Firefly Lane'

The Hollywood star told Us Weekly: "I love these two women, and I loved that they were in their 40s [and it was] a significant part of the story.

"You get to see that trajectory of their lives as young women through up until their 40s and their mid 40s. And it's so beautiful to get to experience a woman's story that way."

The show follows the story of two friends from their teenage years through until their 40s.

But Katherine has admitted that she felt a little anxious about playing a younger version of her character, Tully Hart.

The actress shared: "It was a bit nerve-wracking.

"I was almost 40 when we started to try to play, like, at one point, I think they had us playing 19 in college, and I was like, 'I think you're pushing the envelope a bit.' Like, I get that there's CGI, but ... 19 is different emotionally, too. It's not just how you look. It's how you behave. It's everything.

"So I just remember, like, the first day trying to play Tully at 22 or something, and was like, 'Should I just be bouncier? Should I have more elasticity in my limbs?' Like, I'm stiff. My back hurts. You know, it's just a whole different bag of tricks, but it really brought it to mind, like, oh yeah, you know, ageing is a thing. It's not just about your face and what's happening to your face. It's everything."

Meanwhile, Katherine was previously shunned by Hollywood after she admitted that it was "hard for [her] to love" 'Knocked Up', her 2007 comedy movie.

The actress - whose on-screen character had an unintended pregnancy - told Vanity Fair magazine: "It paints the women as shrews, as humourless and uptight, and it paints the men as lovable, goofy, fun-loving guys.

"Why is this how you're portraying women? Ninety-eight percent of the time it was an amazing experience, but it was hard for me to love the movie."