Diapers can absorb large quantities of pee because of the super absorbent core. It is made up of a powder-like substance that can absorb more than 50 times its own weight of pee in an instant, and has the ability to solidify the liquid into a gel-like texture. The gel does not leak, even if external pressure is applied.

What is the substance that forms the absorbent core?
Put simply, it is formed by combining a mesh-like "molecular chain" with "salt molecules".

Water moves from an area of lower concentration of salt to one of higher concentration of salt. This process is known as "osmosis". In the absorbent core lies an abundant amount of salt molecules. So when the high salt concentrated absorbent core comes into contact with water, the water molecules will diffuse to the core.

Also, the mesh-like molecular chain can maintain its gel form even after absorbing a large amount of water. This is the reason why the absorbed pee will not leak even when external pressure is applied.

The successful research and development of the absorbent core technology has vastly improved the absorption and water retention capabilities of diapers. It has also provided a better solution to leakage or backflow problems. Because less paper and paper pulp are used, diapers are now slimmer and lighter.