For years, beauty chemists have been trying to figure out the most effective way to stabilize vitamin C, a beloved skincare ingredient that tends to be pretty finicky. Korean beauty brand Vitabrid has developed an effective system that stabilizes active vitamin C via its Dual Serum ($75). As the name hints, the product contains two different types of liquid (vitamin C and a peptide complex) that are only combined just prior to use via a twist and shake. Only then are the ingredients activated, ensuring you're getting the freshest product possible.