Stickers can be sticky only if they contain a substance called an adhesive—a kind of glue or paste that makes them stick to a surface. Adhesives can be made from different materials and produced in different ways, but they all work in somewhat the same way by using “macromolecules.” Macro means “big.” These molecules can be thought of as “molecular ropes,” or long strings of repeating molecules.

Certain types of molecules are naturally sticky to one another and to other molecules. In adhesives, the molecular ropes are arranged so that their little sticky parts are all lined up. With all those sticky parts working together, the molecules stick very tightly to one another and to many surfaces.

Chemists and engineers make many different kinds of adhesives and are always working on creating new big molecules that are even stickier—or that are less sticky, when that’s needed, such as for removable stickers.