A macromolecule is a very large molecule commonly created by polymerization of smaller subunits (monomers). They are typically composed of thousands or more atoms. The most common macromolecules in biochemistry are biopolymers (nucleic acids, proteins, carbohydrates and polyphenols) and large non-polymeric molecules (such as lipids and macrocycles). Synthetic macromolecules include common plastics and synthetic fibres as well as experimental materials such as carbon nanotubes.