Cosmetic Science Library

Answering the “why” of
cosmetics, with science.

A library where you learn cosmetic science. Aiming to be the definitive cosmetic-science library.

Explore the Library

342 ingredients

Start from a concern

News

2026.09.15NEWRe-examining the "28-Day Turnover" Myth Through Science 2026.09.12Ingredient Encyclopedia Expanded to 342 Entries 2026.09.08The 4-Week Summer Damage Recovery Blueprint

Ingredient of the Day

The most potent melanin production suppression

Ingredients

Featured Ingredients

Ceramide NP NS AP

Barrier function repair, TEWL reduction

Niacinamide Vitamin B3

Wrinkle improvement, melanin suppression, barrier strengthening, NAD+ precursor

Vitamin A (Retinol)

Turnover promotion, collagen synthesis, wrinkle improvement

Vitamin C (Ascorbic Acid)

Antioxidant, collagen synthesis (cofactor for proline hydroxylation), melanin suppression

Moisturizing, skin softening

Antioxidant (vitamin C stabilization and effect enhancement), brightening

Journal

Journal

Skin Longevity SeriesNEWRe-examining the "28-Day Turnover" Myth Through Science2026.09.15 Skin Longevity SeriesThe 4-Week Summer Damage Recovery Blueprint2026.09.08 Skin Longevity SeriesThe Season-Change Switch: How the Autonomic Nervous System and the Skin Barrier Move Together2026.09.01 Skin Longevity SeriesGrading the Buzzwords of Brightening Skincare2026.08.25 Skin Longevity SeriesThe 3-Day Obon Reset ── A Concentrated Rest Protocol for Sun-Tired Skin2026.08.18 Skin Longevity SeriesThe Invisible Dryness Under Air Conditioning — The Science of TEWL and Barrier Function2026.08.11

Skin Longevity

Don’t fight aging.

KAIAN’s way of rethinking the relationship between skin and time.

READ THE ESSAYS