Metallic materials consist of a microstructure of small crystals called "grains" or crystallites. Misorientation is the difference in crystallographic orientation between two crystallites in a polycrystalline material. A grain boundary is the interface between two grains, or crystallites, in a polycrystalline material. Inside the ferritin shell, iron ions form crystallites together with phosphate and hydroxide ions. It is composed of rod-like apatite crystallites. Such annealing also crystallizes BN, the size of the crystallites increasing with the annealing temperature. It is insoluble, but the crystallites tend to form a colloid. For the misorientation between two cubic crystallites, each possesses its 24 inherent symmetries. The areas where crystallites meet are known as grain boundaries. Lehmann examined the intermediate cloudy fluid, and reported seeing crystallites. The average volume of the crystallites is of order this typical linear size cubed. "Scrub A Dub", credited to The Crystallites. Crystallites are also referred to as grains.