This review is dedicated to the chemistry of Mo iodides. These compounds have a humble origin, and for a long time their chemistry has been almost completely neglected. Although important work on mononuclear and dinuclear Mo iodide complexes was done in 1980–1990s, the situation has dramatically changed within the last decade. The finding that the octahedral Mo iodide clusters are superb long-lived red emitters has triggered numerous publications, not only dealing with various aspects of chemistry of these compounds, but also with their prospects in biomedical, analyitical and other applications. This review comprehensively covers all the developments in the chemistry of Mo iodides from the beginning up to the present.