Plastic wrap, cling film (UK), cling wrap or food wrap, is a thin plastic film typically used for sealing food items in containers to keep them fresh over a longer period of time. Plastic wrap, typically sold on rolls in boxes with a cutting edge, clings to many smooth surfaces and can thus remain tight over the opening of a container without adhesive or other devices. Common plastic wrap is roughly 0.5 mils, or 12.5 µm, thick. In Australia and New Zealand the genericized trademark glad wrap is commonly used, while Saran wrap has become genericized in North America.
Wrapping premature babies in plastic wrap immediately after birth helps prevent low temperature before arrival to the neonatal intensive care unit.
Homogeneity and Heterogeneity are concepts relating to the uniformity in a substance. A material that is homogeneous is uniform in composition or character; one that is heterogeneous is distinctly nonuniform in one of these qualities.
The concepts are the same to every level of complexity, from atoms to populations of animals or people, and galaxies]clarification needed[. Hence, an element may be homogeneous on a larger scale, compared to being heterogeneous on a smaller scale. This is known as an effective medium approach, or effective medium approximations.