For those who have never dealt with the issue, hat hair refers to the matted, mussed, slightly oily mane that your left with after hours (or for some even moments) of donning a cap. Hats may be an ideal means of protecting a blowout from the elements during a commute, sealing in heat during time spent outside, or simply punctuating an outfit, but easing a foreign object over your mane is a surefire means of changing it—for better or for worse. “[Hat hair] is inevitable if you are pressing hair down, plus there's the heat that naturally occurs from wearing something warm on your head,” says hairstylist Justine Marjan.