Glue is a sticky material (usually a liquid) that can stick two or more things together. Glue can be made from plant or animal parts, or it can be made from oil-based chemicals.
The first glues may have been natural liquids that come out of trees when they are cut. Later, people learned to make glue by boiling animal feet, cartilage or bones. Some very strong glues were first made from fish bones, rubber or milk.
A simple glue can be made at home by mixing wheat, flour and water. This glue will stick pieces of paper together. Many kinds of art can be made using glue. A collage is a work of art made by using glue to stick coloured things onto paper.
Some glues can be used to keep water out of boats, buildings or vehicles. In this case, the glue may be called caulk. Some man-made materials, including wood-like materials, are made using glues to bind together small pieces of material or powders.
While many glues are safe, certain kinds of glue contain strong-smelling chemicals. Some people sniff these glues to get high. Sometimes people breathe in the vapors by mistake. This is a very bad idea because these chemicals are often poisons and may cause brain damage or illness.
Glue can also be made from rice or rice flour.