Vermiculite is swollen, heated and expanded mica. It has a laminated structure. It is applied mixed with substrate or surface to maintain the temperature and humidity in germination. It keeps a huge amount of moisture and creates capillarity in the roots. It has excellent cation exchange capacity. It is commonly used in hydroponics, mainly because of their poor aeration. It is mostly used to germinate seeds or root cuttings in other hydroponic propagation units and mixed with other substrates to improve results.