Magnetotactic bacteria (MTB) generate a membrane-enclosed subcellular compartment called magnetosome, which contains a biomineralized magnetite or greigite crystal, an inner membrane-derived lipid bilayer membrane, and a set of specifically targeted associated proteins. Magnetosomes are formed by a group of magnetosome-associated proteins encoded in a genomic region called magnetosome island. Magnetosomes are then arranged in a linear chain-like positioning, and the resulting magnetic dipole of the chain functions as a geomagnetic sensor for magneto-aerotaxis motility. Recent metagenomic analyses of environmental specimens shed light on the sizable phylogenetical diversity of uncultured MTB at the phylum level. These findings have led to a better understanding of the diversity and conservation of magnetosome-associated proteins. This review provided an overview of magnetosomes and magnetosome-associated proteins and introduced recent topics about this fascinating magnetic bacterial organelle. This article is protected by copyright. All rights reserved.