Iron is very important in many biological processes and the ferritin protein family has evolved to store iron and to maintain cellular iron homeostasis. The deletion of the coding gene for the H subunit of ferritin leads to early embryonic death in mice and mutations in the gene for the L subunits in humans has been observed in neurodegenerative diseases, such as neuroferritinopathy. Thus, understanding how ferritin works is imperative and many studies have been conducted to delineate the molecular mechanism of ferritins and bacterioferritins. In the ferritin protein family, it is clear that a catalytic center for iron oxidation, the routes for iron to reach this center and the ability to nucleate an iron core, are common requirements for all ferritins. However, there are differences in the structural and mechanistic details of iron oxidation and mineralization. Although a common mechanism has been proposed for all ferritins, this mechanism needs to be further explored. There is a mechanistic diversity related to structural variation in the ferritin protein family. It is clear that other factors appear to affect the mechanism of iron oxidation and mineralization. This review focusses on the structural features of the ferritin protein family and its role in the mechanism of iron mineralization.