Necrosis is a type of cell death that occurs when cells are damaged or destroyed due to a variety of causes, including trauma, infection, or toxic exposure. It is typically divided into four stages: coagulative necrosis, liquefactive necrosis, caseous necrosis, and fatty necrosis. Coagulative necrosis involves the breakdown of cells, which results in the formation of a mass of hard, coagulated tissue. Liquefactive necrosis involves the destruction of cells, leading to the formation of a soft, fluid-filled cavity. Caseous necrosis is characterized by the formation of a soft, cheesy, and granular mass of necrotic tissue. Finally, fatty necrosis involves the destruction of cells, which results in the accumulation of fat droplets.