Located in the skull, the spermaceti organ is unique to the sperm whale. Its liquid wax was valuable to whalers, as it could be used to make high quality candles and lubricants.
Spermaceti Diagram
Scientists still do not know the precise purpose of the spermaceti organ. It is believed that it controls the whale's bouyancy, to assist it in diving and ascending. It is also possible that the organ is used to amplify and direct the sound waves, that the whale uses for echolocation.