Vitamin B12, also known as cobalamin, is a water-soluble vitamin that plays a key role in normal brain and nervous system function and blood formation. It was first discovered in the late 1920s as the substance that cured pernicious anemia. Vitamin B12 exists in several forms including cyanocobalamin, methylcobalamin, and hydroxocobalamin. It is produced through fermentation by microorganisms but not by plants or animals. Good dietary sources include meat, fish, eggs, and dairy products. Vitamin B12 deficiency can cause megaloblastic anemia and neurological problems if left untreated.