Shellac nails are a form of nail polish—there are more than 100 shades you can choose from at verified salons—developed and patented by nail guru Jan Arnold of Creative Nail Design (CND). The secret sauce of shellac nails is that they combine two types of polish—gel (so your mani lasts long) and traditional polish (which gives your nails shine and a nice pop of color). The formulas bind together when the teeny molecules (called monomers) and larger molecules (called polymers) it’s comprised of are exposed to LED light, creating a shellac effect—hence the term: shellac nails.