system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do some things stay together when wet (sponges, cloth) but others fall apart (tissues, paper)?
gpt
It has to do with what’s causing them to stick together when they’re dry. Sponges are usually one big piece of material. Cloth is made by interweaving long strings. Both of those things might expand if they get wet, but water can’t unweave threads. 
On the other hand, something like paper is made from very fine wood pulp. There isn’t any kind of structure running through the entire sheet: it’s just tiny bits of cellulose stuck together with glucose. When you get paper wet, the glucose, being sugar, is water soluble, so it mixes into the water and stops binding to the cellulose. This means that the paper is just a pile of disjointed wood pulp, and it falls apart.