When it comes to sartorial inspiration, Jenna Lyons holds the key to pulling off pretty much anything. Be it denim on denim for a night out, sweatpants at work, or a white button-down at a wedding — this boss lady flips outfits like Lauren Conrad flips houses. But, at last night's The Avengers: Age of Ultron premiere in New York, the J.Crew creative director convinced us that even a casual T-shirt can be dressed up. The basic in question? Horizontal stripes, with the employment of the 90/10 ratio to clinch the outfit. Let Jenna Lyons be your standing testament to what 90% light and 10% dark looks like IRL. We're pretty positive she didn't have any of those does-this-shirt-make-me-look-bloated conundrums — seeing as she basically runs a multibillion-dollar fashion company and all — but her coat and knee-length skirt are great ideas if you're looking in the mirror and still can't see the signs. The coat stops the stripes from running off left and right while the skirt adds some vertical length to balance out both dimensions. Keep this ratio in mind when it comes to the T-shirts, dresses, and button-ups you reach for when versatility is the word of the day. After all, thinking outside the box (or stripe) is par for the course. Or the red carpet. Or whatever and wherever. You get the point.