Retin-A (Tretinoin) is a vitamin A derivative used to treat acne. Retin-A increase skin-cell turnover and to reduce the tendency for skin cells to stick together. This reduces the formation of acne and allows quicker healing of acne that does develop. Common side effects during treatment, include redness, peeling, stinging, or flashing and may cause increased sensitivity to the sun. Retin-A Micro is formulation uses patented methyl methacrylate/glycol dimethacrylate crosspolymer porous microspheres (MICROSPONGE® System) with more penetration to under skin surface.