Jessica Chastain feels ''vulnerable'' being the face of Yves Saint Laurent because she isn't able to hide behind anybody like she does in her film roles.
The 35-year-old actress believes it is a ''very big deal'' to be the ambassadress for the French fashion house's latest women's fragrance Manifesto, but she also feels more aware of herself in the role because she is used to hiding behind her characters when she stars in movies.
She said: ''For acting, even though I am in my characters, I don't see it as me.
''Having Jessica Chastain be the ambassadress of the fragrance - it's a very vulnerable thing. It's not something I really thought that I would do before until, of course, Yves Saint Laurent called. If you're going to do something like this, it's a very big deal to do it for Yves Saint Laurent.
''But what it does is it makes you very vulnerable because you don't have a character to hide behind.''
The flame-haired beauty admits she's had an affiliation for Yves Saint Laurent ever since she was 12 years old and used to copy her aunt, who wore YSL's Opium scent.
She added to WWD: ''When I was a young girl, I would look at her and think she is so glamorous.
''Everyone else in school was wearing Electric Youth [by] Debbie Gibson, or something really youthful; they smelled like peaches. I came to school wearing Opium, which is so mature.
''It made me feel glamorous; it made me feel grown-up.''