In the movie, Williams plays Monroe, based on memoirs by the late documentary filmmaker Colin Clark (son of Sir Kenneth) chronicling the turbulent story behind the shooting of The Prince and the Showgirl, the 1957 comedy in which Monroe starred opposite Sir Laurence Olivier (played here by Kenneth Branagh) who also served as director.

Michelle, like many young girls, grew up idolizing Monroe from her blonde hair, curvy body and her feisty personality.

“There was just something about that image of her—so lovely and joyful and free. I’ve always thought of her as that woman-child, not an icon, which is probably why I let myself approach the role.”

Taking on such a large role also required Michelle to do her homework and transform herself into all things Marilyn.

“I’d go to bed every night with a stack of books next to me and I’d fall asleep to movies of her. It was like when you were a kid and you’d put a book under your pillow hoping you’d get it by osmosis.”

Michelle even worked to perfect the sex goddess’ signature walk and gained weight to reflect her curvy hips. Despite most of the weight going to her face, the experience was still life changing.

“It felt like being reborn. It felt like breaking my body and remaking it in her image, learning how she walked and talked and held her head. None of that existed in my physical memory, and I knew I needed as much time as possible to make it part of me.”

While she is usually very reserved and even closed off in interviews, she is now boosting about her new life.

“Maybe it has something to do with turning 30. I don’t feel as shy or nervous or self-conscious. I have more confidence that I can handle what life brings me. I don’t feel scared to have an idea and express it.”

My Week With Marilyn hits theaters November 4, 2011.

Check out Michelle’s breath taking photos and the full article in Vogue!