Nanometer particles are important in soils for several reasons. I have chosen particles from 1 to 100 nm as the range for this presentation in one or more dimensions. They are an important part of the clay fraction (< 2 µm) which is the most reactive fraction of the soil. They hold plant nutrients and they influence shrink-swell when measured as the thickness of smectite. Crystals grow in soils as weathering dissolves ions from primary materials and crystals begin to grow. In volcanic glass nanometer size halloysite forms before the glass is dissolved e.g. in the glass of the Pericutin volcano of Mexico that first erupted in the 1940s. A fibrous colloidal halloysiste clay was reported in Australia that has a diameter ca 10 nm and very long and orderly in morphology. Iron oxides are exceedingly small crystals in soils. Ferrihydrite and lepidocrocite crystals grow and dissolve seasonally in rice paddies of southeast Texas. In acid soils goethite crystals are very small partially because of their substitution of Al in the structure that seems to retard crystal growth. Manganese oxide particles form as siderite weathers in soils. Todorokite forms and seems to weather as the chemical environment for growth wanes. Birnessite seems to never grow into crystals beyond very small clay size apparently because the complex composition and the decline in Mn and other favorable ions (possibly Ca and Mg) in solution to permit crystal growth. In more mature soils e.g. Ultisols and Oxisols Fe and Mn oxide crystals grow larger especially in nodules. One could argue that they are not soil in the practical sense. In many soils of Texas there is a small amount of opal-CT that is a mixed structure in the colloid particle size range. Palygorskite and sepiolite occur in some soils in several, isolated parts of the world where these minerals were inherited from the parent sedimentary rocks. These minerals dissolve and apparently reform in some of those soils as very small fibrous particles. Also, in a few places I the world allophane and imogolite form from volcanic materials. These two minerals never grow to particles of coarse clay size. Apparently these two minerals are difficult to disperse and thus complicate their physical properties.