Xylene, also known as xylol or dimethylbenzene, is an organic compound with the formula (CH3)2C6H4. It is derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring, and there are three isomers of xylene: ortho-xylene, meta-xylene, and para-xylene. Xylenes are an important petrochemical produced by catalytic reforming and also by coal carbonization in the manufacture of coke fuel. They also occur in crude oil in concentrations of about 0.5–1%, depending on the source. Xylenes are used as solvents and in making paints, adhesives, and other chemicals. Xylene is widely used in the histology laboratory for tissue processing, staining, and cover slipping. Xylene is a colorless, flammable liquid with a sweet odor. Exposure to xylene can irritate the eyes, nose, skin, and throat, and can also cause headaches, dizziness, confusion, loss of muscle coordination, and in high doses, death. Workers may be harmed from exposure to xylene, and the level of exposure depends upon the dose, duration, and work being done.