The crown of the mammalian tooth is covered with enamel. Enamel is a hard, mineralized substance that is the hardest tissue in the human body. It covers the outer layer of the tooth, known as the crown, and protects it from wear and tear. Enamel is made up of a crystalline structure composed of calcium and phosphate minerals. It is formed by specialized cells called ameloblasts during tooth development and cannot be regenerated once it is lost. Enamel is the first line of defense against tooth decay and cavities. It is not cement, dentine, or caries that cover the crown of the mammalian tooth.