Michelle Williams has revealed she thinks of Marilyn Monroe as "a friend".
Williams said: "How could anyone not be [nervous playing Marilyn]? I kind of ignored it and tried to make her - in my own mind - not a famous person, more like a friend than an icon."
The 31-year-old actress revealed she watched Marilyn's films over and over to help her get into character.
She said: "I read anything and everything that I could get my hands on. The most useful thing was to watch her movies over and over again, to have them in my ears, to make them play like a screen in my mind."
And Williams still counts the films among her favourites, despite watching them over and over again.
She said: "I am very fond of The Prince and the Showgirl still - I can't count the number of times I have seen it! Of course Some Like It Hot and I have special affection for The Misfits as it was a treasured opportunity for her to take on a dramatic role."
My Week With Marilyn is out on 25 November. Watch the trailer below: