Some rare photographs taken between the shoots of 1961 film
, the last film she completed, show a relaxed side of the Hollywood icon, who is synonymous with old Hollywood glamour.
In the newly released images, the actress is dressed-down in a simple white shirt and her hair is plaited in pig tails. She looks sombre but relaxed.
Monroe committed suicide only a year after completing the film, which was written by her ex-husband Arthur Miller. It was directed by John Huston and also starred Clark Gable. The film tells the story of a depressed divorcee's chance encounter with an ageing cowboy.
Other photos also show a fresh-faced Marilyn caught off-guard wrapped in a towel, reading the script between takes and standing at her trailer door sipping coffee as she chats to co-star Montgomery Clift,
These eight intimate images have been captured by photo-journalist Eve Arnold and are on display in the US.
Recalling his association with the star, 98-year-old photographer said: "She was going places but she hadn't arrived. She liked my pictures and was canny enough to realise that they were a fresh approach for presenting her - a looser, more intimate look than the posed studio portraits she was used to in Hollywood.
"It became a bond between us...Marilyn was very important in my career. I think I was helpful in hers too," he added.
Fifty years after her suicide, Hollywood is planning to make a film on the last two years of Monroe with Angelina Jolie playing the troubled star. The film is based on a novel by Andrew O'Hagan The Life And Opinions Of Maf The Dog, And Of His Friend Marilyn Monroe and tells the story of Marilyn's final two years before her death in 1962 through the eyes of her pet Maltese terrier Maf, a gift from Sinatra in 1960.
Born Norma Jeane Mortenson in 1926, Monroe starred in 30 films before her death in 1962.