Retinol is a derivative of vitamin A, it is known for many benefits such as the acceleration of cell renewal  and the neosynthesis of collagen . During the cell renewal process, the cells closest to the surface of the skin die, making way for the younger cells below. This gives the skin a smoother, healthier and younger appearance. However, at high doses, it can attack the skin, which is why, in GREEN KERATIN, retinol is encapsulated, it is retained in small lipid spheres, which reduces the risk of attack on the epidermis  .
 Journal of the American Academy of Dermatology, Volume 36, 1997
 Zasada, M., & Budzisz, E. (2019). Retinoids: Active molecules influencing skin structure formation in cosmetic and dermatological treatments. Advances in Dermatology and Allergology/Postȩpy Dermatologii i Alergologii, 36(4), 392-397
 Journal of controlled release, volume 278, 2018