Over the years, Byrne’s evolved into an actress to watch both on and off the screen. She’s a style icon for chic smart girls, as comfortable in glittering Chanel as she is in sleek Calvin Klein. Her look is youthful but still tasteful, proper but not prim. “There is something very classical in her beauty, but then there is also something very unique to her and the proportions of her face,” says makeup artist Kate Lee, creative director for this month’s Beauty Test and frequent collaborator with the actress. “A little bit like Jean Shrimpton. She’s incredibly easy to imagine transitioning genres and decades. I think her beauty is truly very versatile.”

Of course, like most beautiful women, actresses perhaps in particular, Byrne has a complicated relationship with her looks. “Beauty comes from within. It’s a cliché, but I think it’s true,” says the 35-year-old. “However, in this business, it’s hard to reconcile that when you’re constantly being told things about your appearance, whether it’s that you are too pretty or too plain or too brunette or whatever the problem is.” This thinking is partly what inspired Byrne to co-found an all-female film and theater production company called The Dollhouse Collective, which aims to tell stories that feature strong female leads. “We are developing a script called Seriously Red about a woman who dreams of becoming a Dolly Parton impersonator,” she reveals. Byrne’s own film career, meanwhile, continues to gain momentum. Opening tomorrow, she appears again with Melissa McCarthy in the comedy Spy playing a villainous Bulgarian arms dealer whose iciness off-sets McCarthy’s CIA agent bluster. Further down the pipeline are The Meddler (in which she stars opposite Susan Sarandon) and the latest film in the X-Men franchise, X-Men: Apocalypse. “We're shooting now,” says Byrne, who will reprise her role as scientist Moira MacTaggert. “So lots of mutants in my summer plans.”

Below, Byrne takes a break from her sci-fi escapades to discuss more prosaic subjects like her makeup essentials, the definition of glamour and why she envies boyfriend Bobby Cannavale’s skin.