Eyelash extensions are individual lashes, made of a synthetic fiber such as nylon, which a professional glues one by one to each of your top lashes.
Using long, pointed tweezers, the tech brushes a single synthetic lash in a dab of adhesive. With another pair of tweezers, she separates the natural lashes to isolate just one. She places the synthetic lash on the natural lash, holding it for a few seconds while the glue bonds. The tech repeats the process, one lash at a time, attaching 40 to 100 lashes per eye. The tech will use several lengths of lashes, attaching the longest artificial lashes to your longest natural lashes.
Eyelash extensions last a few weeks to 2 months and fall out when your natural lashes do.