Sienna Miller Debuts an Asymmetrical Bob

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Leave it to Sienna Miller to give the ever-trendy bob an extra edge! Over the weekend, the star was spotted out in London with a graphic asymmetrical cut, which walked the line between a chin-skimming bob and a collarbone-length lob.When it comes to trying out (or starting) the next big trend in hair, Miller has no qualms over changing up her own 'do. She's been a platinum blonde, deep brunette, and just about every shade in between--including pastel pink--and has even chopped her long layers into a pixie to play Edie Sedgwick in Factory Girl. "I'm really not too attached to my hair," she told InStyle previously. "If I worried about what people thought about my look, I'd get it all wrong."

See more celebrity hair makeovers in our gallery!

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Nicole Richie

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After posting an Instagram edited to look like she had purple hair in late February, Nicole Richie was inspired to make the change permanent in March. We can't decide what we like more: The bold color, or the fact that Richie's look mirrors the shade of her latest fragrance, NO Rules.

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Rosario Dawson

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Dawson cut her long strands into a chin-length bob in mid-December.

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Zosia Mamet

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True to her unconventional sense of style, Zosia Mamet took her platinum bob to a steely grey in December.

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Keira Knightley

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The actress kicked off December by taking her warm fawn strands to a deep chocolate hue.

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Kate Upton

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The supermodel fooled us with this faux lob she debuted while on the promo tour for Game of War: Fire Age.

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Vanessa Hudgens

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The star gave her blonde ombre lob a fire-engine red tint.

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Eva Longoria

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Longoria walked the red carpet at the Global Gift Gala in November with a new shoulder-skimming cut.

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Sarah Hyland

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She woke up like this! Using Queen Bey as her muse, Sarah Hyland went solid blonde in November.

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Jessica Alba

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Could another installment of Sin City be happening soon? After seeing Jessica Alba's Nancy-esque solid blonde hue in November, we certainly hope so!

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Hailee Steinfeld

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In November, Steinfeld chopped her mile-long strands into a shorter look that hit just below the shoulder.

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Frieda Pinto

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In November, Freida Pinto cut her signature layers into a collarbone-skimming lob.

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Faith Hill

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The Southern beauty debuted a bold pixie cut at the Country Music Awards in November.

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Beyonce

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From baby bangs, to a bob! Beyonce returned to her chin-length crop in November.

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Zac Efron

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In November, Efron took his trademark crop to an undercut style, which featured shaved sides and long layers on top.

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Cara Delevingne

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The model kicked off November by swapping her honey blonde highlights for a bold brunette hue.

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Ellen Page

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What a change! The actress ended October by chopping her long layers into a dramatic pixie cut.

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Natasha Bedingfield

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Bedingfield chopped off her locks in October, saying it was time for a change.

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Shailene Woodley

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Woodley returned to her natural brunette hue in late October.

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Jessica Simpson

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Simpson hopped on the lob trend in late October when she took her trademark Rapunzel layers to a sleek, colllarbone-length style.

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Lauren Conrad

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We collectively swooned when the style icon debuted a fresh, layered lob in October.

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Lena Dunham

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The beauty and fashion risk taker swapped her short blonde 'do for this minty green shade for the Canadian leg of her book tour.

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Halle Berry

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In a departure from her trademark pixie, Halle Berry debuted a long bob in October.

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Sarah Michelle Gellar

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Buffy got a bob! In late October, Gellar took to Twitter to show off her tousled lob.

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Beyonce

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Suprise! Ever the risk-taker, Beyonce debuted a set of baby bangs while leaving Paris in mid-October.

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Zendaya

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Zendaya made a major change in October, taking her long caramel-toned curls to a dark, graphic bob with blunt bangs.

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Jena Malone

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The Catching Fire star kicked off October by debuting an equally-fiery auburn shade.

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Beyonce

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Beyonce kicked off October with a brand new set of bangs, and no surprise here, we thought they were flawless!

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Shailene Woodley

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The actress attended Paris Fashion Week in October with brand-new blonde highlights.

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Katy Perry

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Believe it or not, this is one shade we haven't seen Perry work before... The star kicked off fall by debuting a Muppet-inspired neon red hue.

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Britney Spears

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Britney got a bob! The star cut her long layers into a sleek, chin-length style in late September.

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Sandra Bullock

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Sandra Bullock ended summer by taking her brunette layers to a sunny blonde hue in late September.

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Elle Fanning

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In late September, the younger Fanning sister swapped her trademark platinum hue for a warm brunette.

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Drew Barrymore

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In September, Drew Barrymore welcomed fall by unveiling her deep brunette hue.