You don't need to be an early adopter in the beauty world to know that serums are no longer just for sorting frizzy hair. For many, they've now usurped poor old toner as the second item in the standard three-step skincare routine. Or that's how they ought to be used – conversations overheard in the beauty hall suggest that a lot of people are still a bit unclear on this, slapping them on instead of moisturiser. In fairness, the word "serum" suggests a magical elixir that will single-handedly rend a hole in the time-space continuum, but really they work more as sidekick than superhero. Good for boosting hydration and plumping fine lines, as well as addressing more specific concerns such as pigmentation, they penetrate skin more quickly than a cream, but need the final seal of moisturiser. Think of them as the extra wheatgrass shot in your smoothie. Actually, don't – they're far better than that.