The sodium polyacrylate that Huggies diapers and other diapers contain is what makes the diaper absorb the pee fast and holds it away from the babies or child's skin so that they don't feel wet.
The Huggies diapers contain around 1.88 grams of the sodium polyacrylate which then swells up when it gets pee on it.
The more pee that gets absorbed by the sodium polyacrylate the bigger the gel swells up which is why a Huggies diaper and any other diapers swell up when they get wet.
The Huggies diapers also contain 6.97 grams of cotton per diaper.
Most name brand diapers do contain the sodium polyacrylate but not all brands of diapers do but still diapers without the sodium polyacrylate are still good diapers.
But the most absorbent diapers are the ones that are made with sodium polyacrylate including Huggies, Pampers, Luvs diapers etc.