Just as fashions come and go, so do beauty trends. One year the focus might be on plumping lips, another on matte skin. Two years later, you’d better make the transition to dewy skin or risk looking out of date.

The big obsession over the past few years has been eyebrows, for good reason.

“It’s the only feature on your face that you can change drastically without plastic surgery. It’s really malleable. You can pluck it, expand it, you have a lot of options and people take great care in grooming their brows,” said Melissa Markoff, author of a tongue-in-cheek survey of famous brows, “Pluck This: An A-to-Z Eyebrow Fantasia.”

“They really change the expression of your face.”

Women who overdo Botox injections on their forehead famously show no expression because they can’t lift their eyebrows.

The book, illustrated by Julia Hartling, features individuals from the worlds of art, fashion and entertainment, known for their brows or lack thereof. Included are artist Frida Kahlo, known as much for her work as for her unapologetic unibrow, and Vogue editrix Anna Wintour, whose signature long bangs hide brows that look oddly unfinished given her exacting reputation.

It takes a humorous look at the amount of energy, money and pain that goes into perfecting the eyebrow, while also celebrating the ways brows express individualism.

Hartling grew up in Tatarstan, Russia, where there is virtually no beauty industry, so she was shocked to discover Americans’ obsession with beauty products. A story Markoff shared with her caught her imagination two years ago.

“I told her how I had overplucked my eyebrows when I was in my 20s, and I had no idea it was bad until I read a story in Lucky magazine that described them as ‘guppy brows,’ a lot of hair near the bridge and really thin near the end. It was really more of a tadpole.”

Now 45, Markoff said she has yet to achieve brow perfection, saying, “I’m just trying to not look awful. Now that I’ve written a book about brows, I feel like people want to get a closer look at mine. I’m so self-conscious anyway, it’s just another drop in the bucket.”

She envies Hartling’s naturally perfect brows. “She doesn’t have to do anything.”

Six years ago, Anastasia Beverly Hills was one of the only beauty brands focusing on brows. Today, most brands offer brow kits, and more long-term fixes are available.

Eyebrow transplants popular in Europe recently arrived stateside with FDA approval. Adapting the technique of harvesting hair follicles used to transplant head hair, the service is available in look-at-me cities such as New York City and Miami (at a cost of about $7,000).

Until transplant services become more widely available, tattoos might suffice. Fighting Eel co-owner and designer Lan Chung, who understands the value of looking camera-ready at all times, said she first got her brows tattooed about three or four years ago after returning home from a day at the beach to find her made-up brows half gone. “My husband didn’t even tell me because guys don’t notice those things. I said, ‘That’s it!’ and made my appointment right after that.”

The brow tattoos, often advertised as “permanent makeup,” gradually fade away in about a year and a half — allowing for changes in brow trends — and cost about $300 to $500. Chung said she wants to try microblading next, a technique that uses a razor-like device instead of a tattoo needle to draw in individual hairs, giving finished brows a more natural look.

Fishcake co-owner Maura Fujihira was the beneficiary of a microblade treatment after traveling to Los Angeles with a friend who had to give up her appointment time at the last minute. Fujihira is pleased with the results, saying, “It’s one thing less to do in the morning.”

Real hair grows back, and at European Wax Centers throughout Oahu, owners are so confident customers will return for removal that they offer every new guest a complimentary service: lip, eyebrow, or bikini line service for women, and an eyebrow, ear or nose service for men.

At the Benefit Brow Bar at Macy’s Ala Moana, there’s a steady stream of clients throughout the day with appointments for a brow wax ($21), brow tweeze ($23) or trim ($6).

There, the process starts with brow mapping, Benefit’s technique for creating the perfect brow by taking an individual’s key features into account. A line map drawn around the brow helps guide the aesthetician while plucking and waxing. Perfection is all about staying within the lines.

The services are not limited to women. Last week, Timmy Cagadas stopped in to have an aesthetician deal with his near-unibrow.

“Girls say if they were on a desert island, the only thing they would do is their brows,” Cagadas said. “That concept is universal, for men too. It cleans up your whole look. For men, it’s brows and hair. For women, it’s brows and lashes.”

Cagadas said he started plucking his brows in high school to clean them up. Now, he opts to see brow specialists because “I don’t trust myself. I don’t want to look surprised. I don’t want to look angry.”

Benefit aesthetician Victoria Wenning said the recent fetish over eyebrows is largely social-media driven. “People are highly influenced by social media celebrities like the Kardashians. Over time people started to notice they have really beautiful eyebrows.”

While the idea of the perfect eyebrow is tailored to fit an individual, the overall characteristics are brows that are well-shaped and clean, without stray hairs, then filled in with color to accentuate shape and frame the face and eyes.

This applies to regional differences as well. Koreans favor a straight, caterpillar-style brow that gives the impression of untamed youth, while Americans favor a sophisticated, womanly arch.

Another poster child for must-have eyebrows is British model Cara Delevingne, whose bushy, defined brows make her the Brooke Shields of today’s generation. Some might prefer to follow her lead. Her beauty secret? She does nothing to her brows.