A monomer is a small, simple molecule that can join together with other monomers to form a larger structure called a polymer. This process of linking monomers is known as polymerization. Monomers can be found in various forms, including natural substances like sugars and amino acids, as well as synthetic materials like plastics. Monomers play a crucial role in many biological and industrial processes. For example, in the case of proteins, the monomers are amino acids, which combine to create complex structures essential for life. In the world of materials, monomers like ethylene are used to produce polyethylene, a common plastic found in everyday items.