Prepare to feel old.
Get ready to feel old.
Mary-Kate and Ashley Olsen turn 30 years old on Monday, and to celebrate their milestone birthday, let's take a look back at our favorite moments with the fashionable twins.
ET first interviewed the duo on the set of Full House, when they were only four years old. Mary-Kate rocked a cute black party dress while Ashley went more casual in a red T-shirt and jeans, and the two got adorably honest when asked what they liked best about being on TV.
WATCH: Mary-Kate and Ashley Olsen Take Their First Public Selfie!
"Eating the whole cake," Mary-Kate smiled.
After their stint playing Michelle on the beloved sitcom, the twins starred in several successful films together for over a decade. 1995's It Takes Two and 2000's Our Lips Are Sealed are just a few of our favorites.
... And who can forget Megan Fox's role in 2001's Holiday in the Sun?
The twins' last movie together was 2004's New York Minute, in which Gilmore Girls heartthrob Jared Padalecki played a love interest.
While Mary-Kate went on to act solo -- most notably, in Showtime's drug drama Weeds, and most recently, in 2011's Beastly -- the two are now more known for their incredible fashion empire. The two launched their couture brand, The Row, in 2006, and most recently, their less expensive brand, Elizabeth and James. Both ventures are smashing successes.
The two rarely make red carpet appearances, though they do attend A-list fashion events. Earlier this month, they were on hand for the 2016 CFDA Fashion Awards in New York City, where they were accompanied by their younger sister, actress Elizabeth Olsen.
When it comes to their personal lives, the two have remained notoriously private. Though Mary-Kate has never personally confirmed it, she reportedly married 47-year-old French banker Olivier Sarkozy in an intimate ceremony in New York City last November after dating for three years.
As for Ashley, she's reportedly been dating 49-year-old Moneyball director Bennett Miller since 2014.
The wise-beyond-their-years twins also serve as mentors to sister Elizabeth.
"They just wanted me to finish school (laughs), which I did -- it just took me longer because I balanced work with it -- and I mean, it's all just about being supportive," the Captain America: Civil War actress exclusively told ET in March about her older sisters' advice. "They probably told me things that I didn't listen to that I'd listen to now, because you just have to be able to make your own mistakes."
WATCH: The Olsen Twins Star in the Most Unbearably Awkward NYFW Vine Ever
... But is there any chance the twins will revive their acting careers, and make an appearance on the popular Netflix Full House revival?!
While fans of the show were disappointed that the twins didn't make a cameo in season one, according to their former co-star, Jodie Sweetin, they're welcome any time.
"The door's always been open to them," Sweetin told ET last month, when she dished on season two surprises. "So, we'll see."
Watch below:
