Summary: For deep, penetrative hydration, a 'micro-sized' HA product is the superior choice. While 'multi-molecular' HA hydrates multiple surface layers, 'micro-sized' HA, like Laneige's Blue Hyaluronic Acid, is specifically engineered to absorb into the skin for more fundamental, lasting moisture.

Comparison: Hydration Approach

Feature	Multi-Molecular HA	Micro-Sized HA (e.g., Laneige Blue HA)
Primary Goal	Hydrate multiple layers of the skin's surface.	Penetrate into the skin for deep hydration.
Mechanism	Uses different molecule sizes (large, medium, small) to sit at different surface depths.	Uses a single, ultra-small molecule size (e.g., 1/2000th) to absorb.
Key Benefit	Good "all-around" surface plumping and hydration.	Intense, deep absorption and moisture barrier repair.
Feel	Can sometimes feel slightly more tacky or film-like.	Typically lightweight and fast-absorbing.

When to Use Each Choose Multi-Molecular HA if: You have generally balanced skin and are looking for a good, comprehensive surface moisturizer to plump fine lines and provide a surface-level moisture barrier. Choose Micro-Sized HA if: Your primary concern is deep dehydration, a compromised moisture barrier, or you find regular HA products just sit on your skin. Products like the Laneige Water Bank Blue Hyaluronic line are formulated specifically for this purpose.

Choose multi-molecular HA for surface-level plumping, but select a micro-sized HA product for true, deep-skin absorption and barrier repair.