Topological insulators have emerged as a major topic of condensed matter physics research with several novel applications proposed. Although there are now a number of established experimental examples of materials in this class, all of them can be described by theories based on electronic band structure, which implies that they do not possess electronic correlations strong enough to fundamentally change this theoretical description. Here, we review recent theoretical progress in the description of a class of strongly correlated topological insulators - fractionalized topological insulators - where band theory fails dramatically due to the fractionalization of the electron into other degrees of freedom.

5 pages, 3 figures. Published version