The word “teratology” is derived from the Latin meaning “the study of monsters.” It is actually the study of congenital malformations, which started with the study of the correlation of German measles to birth defects. Later, there was an industrial link to teratogens discovered involving the chemical methyl mercury. Results of exposure to teratogenic chemicals on living organisms include the alteration of developing cells, leading to improper functioning of these cells. This may result in the death of the embryo or fetus. Specific types of birth defects can be caused by specific types of chemicals. These chemicals do not permanently damage the reproductive system, and normal children can be produced as long as repeated exposure does not occur.