Necrosis is the dying of tissue. Whether from frostbite, disease or other causes, the cells, most visibly skin cells, begin to die. They can then release chemicals that may harm or kill surrounding cells. If the cells are not removed, skin can be lost from entire limbs. After the skin blackens, it will simply fall off, resulting in exposed bone, or in areas like the ear, nothing will remain. Also known as gangrene.