Layering order matters: apply products from thinnest to thickest texture so each can absorb before the next seals it in.
A general rule — water-based serums (like Hyaluronic Acid) go before oil-based ones; active treatments (Vitamin C, retinal, niacinamide) go before richer creams. Wait 60–90 seconds between layers, and never combine Vitamin C with retinal in the same routine step — alternate them AM/PM instead.
Moisturizer and SPF always go last.