If substances, small particles or biocatalysts and intact cells bind to a solid matrix, this process is called immobilization (lat. immobilis = immovable). Thus, e.g., the spatial fixation of bacteria, cells or enzymes in gel particles, capsules or defined reaction spaces are referred to as immobilization. Immobilization plays an important role in soil nutrient dynamics. It causes soil nutrients to be available in a temporarily fixed form, such as in microorganisms or rocks. Only when conditions change – such as the dying of microorganisms or weathering of the rock – they are released or mobilized again.