Vitamin C serum is a topical skincare product containing a high concentration of ascorbic acid, the active form of vitamin C. It provides numerous benefits for the skin, including increased collagen production, reduced signs of aging, improved skin tone and texture, and protection against sun damage. Vitamin C is an unstable molecule that can easily degrade when exposed to light, heat, and air Maintaining a low pH (below 3.5) is crucial for stabilizing vitamin C in serum formulations and enhancing skin penetration. The efficacy of vitamin C serum is directly proportional to its concentration, with 20% being the maximum effective level. Regular application of vitamin C serum can lead to a tenacious reservoir in the skin, providing long-lasting photoprotection. However, not all vitamin C derivatives used in cosmetic products are physiologically effective, as some may not be adequately delivered into the dermis or converted to the biologically active form. This project aims to develop a stable and effective vitamin C serum by improving the extraction and quantification methods .The stability and skin penetration of the serum will be evaluated under different storage conditions and application methods. The findings of this project will contribute to the development of improved vitamin C-based skincare products with enhanced efficacy and stability.