Polymerization is a chemical process where small molecules, called monomers, join together to form a larger, more complex structure known as a polymer. This process can occur in various ways, including addition and condensation reactions. Common examples of polymers include plastic, rubber, and DNA, which play essential roles in everyday life and biological functions. During polymerization, the properties of the resulting polymer can vary greatly depending on the type of monomers used and the conditions of the reaction. For instance, polyethylene, a widely used plastic, is created from the polymerization of ethylene monomers. Understanding polymerization helps scientists develop new materials and improve existing ones.