Aluminium foil, or tin foil, is a paper-thin, shiny sheet of aluminium metal. It's made by rolling large slabs of aluminium until they are less than 0.2 mm thick. It's used industrially for a variety of purposes, including packing, insulation and transportation. Aluminium foil provides a complete barrier to light, oxygen, moisture and bacteria. For this reason, foil is used extensively in food and pharmaceutical packaging.