We always thought stretch marks were something us nameless commoners experienced and never perfect, thin supermodels. That is, until Chrissy Teigen posted this Instagram back in April 2015 of what have arguably become the most famous stretch marks on the Internet.

"Stretches say hi!" captioned the "Sports Illustrated" model of her comfortingly normal-looking thighs. For its stripped-down realness, this beauty Insta lands in the No. 9 spot on our list. (Though if we were ranking nicknames for stretch marks, we're pretty sure it'd be No. 1.)

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Kardashians and makeovers are two of the Internet's favorite things, so it's no surprise that the Insta-universe freaked when Kim K revealed she'd gone platinum blonde overnight back in March for Paris Fashion Week.

Kim didn't keep the look for long, but we were obsessed with it while it lasted. Colorist Lorri Goddard nailed the ashy platinum color (tricky to achieve, coming from ultra-dark brunette), making this one of the most memorable hair color makeovers of 2015.

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Instagram's "Free the Nipple" campaign blew up late last year thanks to support from celebrities like Rihanna and Cara Delevingne. But leave it to the 15-year-old daughter of Will and Jada Pinkett Smith to post the most attention grabbing nipple 'gram in January of 2015.

Shining a light on the debatably sexist Instagram regulation to flag photos of women's (but not men's) nipples, Willow posted this portrait of herself in a conservative turtleneck printed with the image of a topless woman. The post inspired a category 3 hurricane of controversy surrounding Willow's age, which in itself begs the question: Exactly how young is too young for someone to question anti-feminist policies while not actually showing her boobs?

Controversial or not, we're pretty fascinated by the Smith children and have not forgotten this Instagram post nearly a year later.

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When the bewildering #ThighBrow trend surfaced late this summer, half of us rolled our eyes hard and half of us finally found our favorite hashtag of the year. (We're still going back and forth.)

Rebelling against the unattainable thigh gap, the #ThighBrow (not to be confused with #EyebrowsOnFleek) refers to the folds at the top of each thigh that might curve around a high-cut bikini bottom, basically signaling that one has a big booty.

#ThighBrow was (and continues to be) absurd, but we have a love-hate relationship with these sort of hyper-specific Instagram trends. We don't necessarily expect #ThighBrow to come back next year, but as a 2015 Insta-trend, it deserves to be remembered.

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Okay, so we're a little biased about this Instagram post. But most of us can probably agree that Gwen Stefani and Urban Decay announcing their new makeup collaboration was one of the year's most exciting beauty moments.

Only six Instagram accounts in the world got to break the news, and @TotalBeautyEditors was one of them. We've since gotten our hands on Gwen's highly anticipated eye shadow palette (which launched and then promptly sold out on November 22), and it has made us all the more excited for the rest of the collection.