When Sienna Miller tripped onto a red carpet in Rome, the fashion world gasped as one. The English rose was sporting caterpillars: Heavy, dark eyebrows.
"Personally I think they look hideous," said Vaishaly Patel, London's eyebrow shaper to the stars. "When you've got blond hair the number one rule is not to have black eyebrows. I think they're a lovely shape but just on the wrong person."
So, there is a right person. Bushy is back as far as eyebrows are concerned. So, poor Sienna was just trying to follow fashion. It's just that not every fashion suits everyone. For example, I look dreadful in skinny jeans.
For this apparently lowbrow issue, there's some highbrow analysis. Eyebrows tell a story of cultures, eras and politics. For example, in Iran "un-groomed" is a sign of virginity. The Mexican artist Frida Kahlo sported a unibrow. It became her signature, an expression of independence and feminist strength.
In Western celebrity culture we can trace the ebb and flow of the eyebrow. In the 1940s and 50s, female movie stars often removed their eyebrows completely.
"Eyebrows, any body hair, anything suggestive of masculinity had to be immediately erased," explained Zoe Williams, a zeitgeist columnist with The Guardian newspaper. "There was a real interest in ramming home the difference between the genders."
Why? Was it a conscious effort to redefine femininity after the austerity of the war years? Who knows. But check out Ronald Coleman's slugs and Marlene Dietrich's sliver in Kismet, and you're left in no doubt who's man, who's women and the gulf between.
"Then in the 60s, everything got a lot more androgynous," continued Williams. Hair grew everywhere for years. It sprouted all over men and women. The bushy brow's zenith was reached on Brooke Shields' face in The Blue Lagoon.
Society's evolution can be traced through the eyebrow. In the 80s eyebrows thinned again, reflecting the self-obsession and greed of the age. Power suits, shoulder pads, enormous cell phones and scary, mean, thin eyebrows. Watch Wall Street. You'll see. Women were groomed to within an inch of their lives.
In the "noughties" we're supposed to be caring, sharing, green, concerned. So to reflect that, eyebrows are getting bigger. More natural.
There's a backlash against the over-plucked brow, according to Jaimineey Patel, manager of a Blink Eyebrow Bar in London. Patel and a phalanx of eyebrow "threaders" are in the trenches, persuading clients to grow back their brows before they gently shape them with twisted thread held between their teeth.
"We always do a thorough consultation," explained Patel. "We ask them what they want out of their eyebrows." What can you want from an eyebrow? More than function, apparently. More than a sponge effect to keep sweat out of your eyes.
Apparently they frame your face. "To be honest," confided Patel. "A lot of clients feel they've had a facelift because it opens your eyes out."
Eyebrows are the new window on the soul. So be careful Sienna, those caterpillars may reveal more than you want us to know.