Magnetite crystals produced by magnetotactic bacteria (MTB) have uniform species–specific morphologies and sizes, which are mostly unknown from inorganic systems. This indicates that biomineralization in magnetosomes is a process with genetic control over the accumulation of iron, the deposition of the magnetic crystal within a specific compartment, as well as their intracellular assembly and alignment into chain-like structures. Our understanding of the molecular and genetic basis of magnetosome formation has substantially improved during the last few years due to the progress in genome analysis and the development of advanced genetic techniques to study MTB.