Elle Fanning admits playing Mary Shelley proved to be a unique challenge.

The 20-year-old actress stars as the iconic writer - who is best known for her Gothic novel 'Frankenstein; or, The Modern Prometheus' - in the period-drama about Shelley's life, and Elle has revealed how the movie-making process has changed her outlook on life.

She confessed: ''I felt like Mary Shelley taught me how to be a woman in a way. I don't know, [she taught me] a little bit of womanhood.''

Despite this, Elle admitted it was a challenge having to play Shelley, because there was no audio or video footage to guide her performance.

The novelist was born in 1797 and so even though she's one of the world's most revered literary figures, Elle didn't have many points of reference while making the movie.

Speaking to ITV's 'Lorraine', she shared: ''Definitely a challenge because you can't look like a painting of her. There's not a video of the way she moves or the way she talks.

''It's also a love story, you know? I also think it's a relationship of people who relate to one another that's messy and not perfect.''

Meanwhile, Elle previously revealed she considers the movie to be a milestone in her life because it was the last film she made before graduating from high school.

She explained: ''When I filmed the movie, I was 17, about to turn 18.

''This was the last movie that I had to do school on the set. It was a milestone movie for me. I really felt wiser and more mature after.''