Eyelash growth serum works with your natural hair follicle to produce thicker and fuller natural lashes over time. This can be used in conjunction with eyelash extensions to create an even fuller look. Lash Serum is applied to the base of your lashes twice a day, until desired results are obtained. Lashes will start growing longer and thicker immediately, but will take 4-6 weeks to see optimal results. To maintain these results use the serum 3-5 times per week.