Ferritins are a superfamily of iron-storage proteins that are found in all living organisms with the exception of yeast. They are ubiquitous, iron-binding proteins that play an important role in cellular iron homeostasis. This book discusses topical research in the study of the functions, biosynthesis and regulation of ferritin. Topics include ferritin as an iron source for pathogens and as part of the antioxidative machinery in plants under stress; the antioxidant role of ferritin and transferrin in elite athletes; ferritin and ferroxidase activity and increased serum ferritin in morbid obesity and bariatric surgery.