The year was 1991—ponytails hung high, bows were affixed to practically everything, and Mary-Kate and Ashley Olsen were first making a name for themselves playing Michelle Tanner on Full House. Over the next two decades, the twins grew up, grew out their bangs, and experimented with ever-changing beauty statements both on and off screen. And while there’s no denying the sophistication of their present-day look, those who have been tracking the sisters for the better part of four decades may find themselves reflecting on many a scene-stealing twinning moment.

There was that time when Mary-Kate became a brunette and broke the girls’s classic mirror-image sibling style. Teens everywhere flat-ironed their hair to mimic the twins’s early-aughts center-parted lengths. And who could forget those revealing halter tops, Ashley’s piece-y crown braid, or Mary Kate’s paparazzi-worthy red lip?

As they’ve built a successful quiet luxury-led fashion empire known to all as The Row, the Olsens’s beauty looks have doubled-down on their tried-and-true beauty formulas. Whether they’re out and about, trying to be low-key on both east or west coasts, or stepping out for a fashion week presentation, the duo will no doubt be sporting the honey blonde hair, bushy brows, glowing skin, and perfectly calibrated nude makeup that have become their signatures.

Year after year, Mary-Kate and Ashley Olsen have distinguished themselves as enduring beauty and fashion icons. In honor of their 40th birthday, Vogue looks back at their 40 best beauty moments—from (many!) Met Galas to movie premieres, street style moments, and fashion week front rows. Scroll below.