Polymers are molecules formed of components, so-called monomers, composed of any number of repeated sub-units. Polymers are also referred to as ‘macro-molecules’. Polymers can be linear chains of monomeric base elements, but they can also branch off, use the branches to connect to neighbouring chains (crosslink), form rings or crystalline structures. Organic molecules are of particular importance, i.e. molecules which themselves or their basic constituents are formed by living organisms and have as their main constituents hydrogen atoms obtained from water and carbon atoms obtained from carbon dioxide in the air. The carbon can form polymer chains via one or two bonds and then still has 2 or 3 valence electrons available to form further bonds. However, there are also polymers or macromolecules which are not based on carbon compounds (inorganic polymers).