The term “Migration” refers to the diffusion of a group of substances from a zone of higher concentration (the layer of packaging material in contact with the food) to a zone of lower concentration (the surface of the food). The migration of chemical substances is a very complex process and depends on several parameters, such as the concentration of the substances in the packaging and in the food, the nature of the food, the temperature and the duration of contact. Depending on how it is defined, it is categorized into total and special migration.