For application instructions, please see the Youth Serum packaging. Unlike most iS Clinical serums, Youth Serum calls for an application of only 1-2 drops, that should be evenly and gently glided over the area. Do not glide over the area of application continually, or attempt to rub the serum in. Due to the gel-like texture of this product, if over applied or applied with friction, it will not absorb properly and cause pilling. If applied correctly Youth Serum will absorb immediately, with a tightening and firming feeling to follow.