A lot of people have attempted to break down exactly what makes an It girl an It girl and come up short, but I think Sienna Miller just answered the age-old question. In my opinion, it’s all about maintaining the delicate balance between versatility and consistency. A true It girl can wear a fresh-off-the-runway Erdem gown one day and jeans and a graphic T-shirt the next and look natural and comfortable in both. She makes everything look effortless, whether it is or not, and every outfit she wears becomes an instant Pinterest board inclusion, including the one she just wore in New York City to join Jimmy Fallon on The Tonight Show.

For the appearance, Miller, who is currently doing press for her new HBO series War, kept things simple, donning a vintage Lou Reed graphic T-shirt tucked into a pair of vintage Levi’s 501s. She finished off the chic early-fall ensemble with a pair of strappy sandals, proving that sometimes less is more.

On Sienna Miller: Levi’s jeans