The small molecules that form links in polymer chains are called monomers.

Here's a breakdown:

* Polymer: A large molecule composed of many repeating subunits.

* Monomer: The small, repeating unit that makes up a polymer.

Think of it like building a chain out of paper clips. The paper clips are the monomers, and the chain itself is the polymer.

Here are some examples of monomers and the polymers they form:

* Ethylene (monomer) --> Polyethylene (polymer)

* Glucose (monomer) --> Starch (polymer)

* Amino acids (monomers) --> Proteins (polymers)

The process of joining monomers together to form polymers is called polymerization.