Growing media, also known as a growing medium or substrate, is the material used in a container to grow a plant. It serves three primary functions: providing physical support for the plant, facilitating root growth, and delivering nutrients, water, and air to the plant through its roots. Growing media consist of mixtures of components that provide water, air, nutrients, and support to plants. The physical characteristics of a growing medium are determined by the components used and the proportions in which they are blended together. The components used in formulating growing media can be either organic or inorganic. Organic components include peat moss, bark, coconut coir, rice hulls, and wood fiber, while inorganic components include perlite, pumice, vermiculite, sand, and hydrogel. The composition of a growing medium should be largely determined by the crop being produced. Manufacturers also need growing media to be physically and chemically stable from the time of production until the time of use. The bulk density of the ingredients used is also important because this affects transport costs, a major part of the total cost of production and delivery to the end customer.