Soil structure affects the abilities of soil to retain and release water, air, nutrients and minerals. When soils have a good structure, the particles are drawn together in small clumps, or "crumbs." Soils with good "crumb structure" allow the absorption and release of more air and water - in other words, the soil breathes. Soils with poor crumb structure do not have good nutrient exchange, and the plants and animals which depend on it will not thrive.