When you apply lotions or creams to your skin, some of the moisture passes through the stratum corneum, but not all of it. This layer is home to many minor skin imperfections like fine wrinkle lines and blemishes.

All of the action in microdermabrasion takes place at the level of the stratum corneum. Since it only really targets the epidermis (and not the dermis), it is more accurate to call it micro-epi-dermabrasion. Affecting deeper layers of skin would be painful and harmful, and it would risk permanently embedding the tiny grains into the skin.