At the most basic level, eyelash extensions are individual lash fibers which, when applied to your natural lashes, have the effect of thickening, filling out, and extending your eyelashes for a lush and full, glamorous look. Eyelash extensions can be made from synthetic fibers or natural fibers, like mink fur, and are often applied by a makeup artist or lash artist using lash adhesive and specialized tools. These days, there are many types of lash extensions, and they vary in quality, safety, and visual effect.