From that chartreuse Dior gown at the 1997 Oscars, to her recent turn in edgy Mugler at this year’s Grammy Awards,Nicole Kidman has proven herself to be a true fashion force throughout her decades-long career. But, while the statuesque Australian actress might prefer column dresses and modest necklines on the red carpet, her on-camera costumes skew far more unpredictable. The star has perfected the art of transformation—slipping into dowdy floral dresses as Virginia Woolf in The Hours, utilitarian Civil War-era layers in Cold Mountain, or the intricately embellished dance ensembles in Moulin Rouge!—and she’s pulled off each one effortlessly.

On Monday night, Kidman revealed the stories behind some of her most famous outfits during Vogue’s discussion at the Metropolitan Museum of Art. Not surprisingly, the actress and Vogue’s August cover star told editor Hamish Bowles that her love for costumes goes way back to before she was a movie star. She dressed her Barbie dolls in bespoke outfits as a child (handmade by her grandmother) and sported an over-the-top vintage flapper dress to her high-school prom. These days she works with some of the most acclaimed costume designers in Hollywood, including Catherine Martin and Ann Roth.

For Kidman, getting into the right sartorial mindset requires being a completely blank slate for the costume designer. Rather than having a preconceived idea about the character’s outfits, Kidman said she enjoys “letting myself morph into something else.” This could sometimes be a self-described “robotic doll,” like in Stepford Wives (the mini-dresses weren’t her favorite outfit, she laughed). Other times, she drew from her own closet, like the sexy Galliano dress that she famously dropped to the floor at the beginning of Eyes Wide Shut. While Kidman’s eyes lit up when she remembered the elaborate costumes in Moulin Rouge!, she said the 2001 musical was also her most demanding. Not only did she dye her hair 10 shades of red in order to get the ideal hue for Satine, she had to squeeze into a corset with a broken rib (and swears she didn’t complain even once).

This all-or-nothing approach to costumes extends to the clothes you can’t see on camera. Kidman believes that everything, even lingerie, needs to be in character. “Great costume designers do great underwear,” she said. “You’re becoming the character at 6 AM when you put it on.” How’s that for method acting?