Sienna Miller's Gown Wants to Know, "How Low Can You Go?"

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Sienna Miller wore a black velvet gown that nearly plummeted to her belly button at the 81st Venice International Film Festival on Friday, Sept. 6. The dress was vintage Giorgio Armani but the design felt right at home on a red carpet peppered with plunging necklines. Even Lady Gaga chose a plunging Christian Dior Haute Couture gown to walk the Joker: Folie à Deux red carpet with fiancé Michael Polansky. Julianne Moore also got the memo in time to commission a gold sequin gown with long sleeves and—yes—a deep V-neck from Bottega Veneta.

But the trend didn't stop there. Across the globe, Dakota Johnson was busy delivering her bohemian spin on the deep V-neck at the Bulgari Studio Party during New York Fashion Week, pairing a chocolate brown lace slip dress with an oversized pendant. Then, the very same night in Los Angeles, Meghann Fahy and Nicole Kidman both turned up in clavicle-baring gowns for the premiere of their new Netflix series The Perfect Couple. Styled by Jason Bolden, Kidman opted for a shimmering, semi-sheer Ferragamo halter dress. Fahy and stylist Thomas Carter Phillips, on the other hand, selected a black lace dress from Victoria Beckham.

Miller accessorized the stunning velvet number with a pair of strappy slingback sandals from celebrity-beloved brand Aquazzura.

Often, stylists choose to let the deep V-neck shine by leaving the chest otherwise bare. Miller, however, topped off her take on the trend with a lotus-shaped diamond pendant necklace and a chunky diamond cocktail ring, both courtesy of De Beers. But in a clever added touch, the actor balanced out her mega-glitz jewelry by throwing on a pair of round black sunglasses. And thank goodness she did, because I'm obsessed with the tension between that stunning $80,000 necklace and her mysterious mob wife shades.

Miller further accessorized the stunning velvet number with a pair of strappy slingback sandals from celebrity-beloved brand Aquazzura.

Is clavicle the new side boob? Maybe it would be more accurate to say "no bra" is the new "no pants." It's too soon to be definitive, but the New York Fashion Week runways are certainly making a strong case for the trend with plunging necklines popping up at the likes of Ralph Lauren and Grace Ling. The true test, of course, will be to see whether any of those looks make the plunge from catwalk to the Emmys red carpet on September 15.