Mainly Wool known as protein and animal fiber. Wool comes form fibrous covering of goat, camel, sheep etc. The structure of wool fiber is very complex. Diameter of wool fiber can be varying from 18-40 µm along its length.
Every wool fiber can be divided into three sections:
1.     The Root: The living part of the root is situated in the surface of the skin.
2.     The shaft/stem: It is cylindrical and tapers to a point at its free ends.
3.     The tip: Naturally pointed and the free end of the fiber.
Wool Fiber consists of three layers:
1.     Cuticle (Outermost layer)
2.     Cortex(Inner layer)
3.     Medulla
Cuticle is the outermost layer of wool fiber. Generally Cuticle known as Scales. From the action of external force cuticle protects the wool fiber. Cuticle also has some several layers which are converted with a hydrophobic outer layer called epicuticle. Epicuticles have many microscopic pores.
The main part of wool fiber is cortex which is situated under the cuticle and cortex consists of micro fibrils of keratin. Cortex cells vary from 100-200 µm in length, 2.5 µm in width and 1.3 µm in thickness. Cortex is also composed in two sections:
1.     Ortho cortex
2.     Para cortex
Medulla is the central stream cell which is along with the length of the wool fiber. It is mostly coarse.  It is causes some deterioration of fiber quality such as fiber strength is very low, spinning properties lower, higher shade produced.