In chemistry and biology, a macromolecule is defined as a molecule with a very large number of atoms. Macromolecules typically have more than 100 component atoms. Macromolecules exhibit very different properties from smaller molecules, including their subunits, when applicable.
In contrast, a micromolecule is a molecule which has a small size and molecular weight.
The term macromolecule was coined by Nobel laureate Hermann Staudinger in the 1920s. At the time, the term "polymer" had a different meaning than it does today, or else it might have become the preferred word.
Most polymers are macromolecules and many biochemical molecules are macromolecules. Polymers consist of subunits, called mers, that are covalently linked to form larger structures. Proteins, DNA, RNA, and plastics are all macromolecules. Many carbohydrates and lipids are macromolecules. Carbon nanotubes are an example of a macromolecule that is not a biological material.