If you're creating the look with nail polish (the look can be done with ink and even Sharpies), Elle said that the look has to be done in layers. "[The colours need] to be dragged, or marbled, in order to blend the layers," she said. "Using a clean detail brush (like the ones in the Professional Nail Art Liner Brush UV Gel Painting Acrylic Nail Brushes Striping Brushes ($7) set) or even a toothpick, drag through the polish to blur the lines. Be very careful with the colours you choose as the wrong colours can muddy the designs."