Several years ago they made for the perfect novelty selfie but the sheet mask has returned in a more serious sense. Made with paper, cotton or gel, and designed to mimic the shape of a face, each mask is laden with a purpose-driven serum, with hydrating elements such as hyaluronic acid or formulas that pack a collagen-infused punch. A convenient, no mess, all-done-for-you beauty buy you really ought to invest in, they are the ideal quick fix before a night out. Here, we round up the best.