Every celeb has their own signature look, but when it comes to one particular star, it’s all about going retro, all day, nearly every day.

In the case of actress Reese Witherspoon, it’s all about effortlessly chic side-swept hair. And according to celebrity stylists, this simple hairstyle is always on-trend because it easily transforms bland strands into touchable tresses.

“Its popularity stems from the recent vintage hairstyles that are out, particularly the retro waves from the 1940s,” says celebrity hairstylist Amanda Shackleton. “Wearing your hair down, especially for a long event, won’t have much staying power, resulting in your hair looking flat and messy in a few hours. By taking your hair and pinning it over to one side, it takes the weight out of the style and keeps it protected from going flat.”

For ladies who have fine hair, like the 38-year-old Oscar-winner, stylists believe the side-swept look works especially well, as it adds some much-needed oomph to any mane.

“This particular style gives the appearance of hair being fuller and thicker,” says celebrity hairstylist Chaz Dean.

So how does one create the perfect side-swept, à la Witherspoon? Her stylist, Adir Abergel, told InStyle magazine that you should first create a part at the arch of the brow, which he calls "the most flattering placement for a side part." Then, blow dry with a round brush until waves are smooth, pull hair over one shoulder, and add some finishing spray."

"Mist two bobby pins with spray, then cross them behind the ear," Abergel adds.

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