Vitamin B12 (cyanocobalamin) is a water-soluble cobalt-containing corrinoid essential for red blood cell formation, neurological function, and DNA synthesis. It features a corrin ring with a central cobalt ion coordinated to a cyano group, a dimethylbenzimidazole nucleotide, and various side chains. Humans obtain it primarily from animal products or supplements as plants do not synthesize it. Deficiency leads to pernicious anemia and neurological disorders. It is stable in acidic conditions but sensitive to light, heat, and strong oxidizing agents. Industrially produced via bacterial fermentation, it serves as a food fortificant and therapeutic agent for B12 deficiency.