Time has a way of turning items once considered 'uncool' into the trendiest pieces you can own. We've seen it happen with gray sweatpants, chunky sneakers and knit cardigans, so it's no surprise that one of today's must-have accessories is a hat our dads wore throughout the '90s. Polo Ralph Lauren baseball caps are a fashion staple in the celebrity world, with Jennifer Lawrence, Nina Dobrev and Kendall Jenner rocking them on repeat over the past few years.