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Three-dimensional topological insulators (TIs) are a perfectly tunedquantum-mechanical machinery in which counter-propagating and oppositelyspin-polarized conduction channels balance each other on the surface of thematerial. This topological surface state crosses the bandgap of the TI, andlives at the interface between the topological and a trivial material, such asvacuum. Despite its balanced perfection, it is rather useless for any practicalapplications. Instead, it takes the breaking of time-reversal symmetry (TRS),and the appearance of an exchange gap to unlock hidden quantum states. Thequantum anomalous Hall effect, which has first been observed in Cr-doped(Sb,Bi)$_2$Te$_3$, is an example of such a state in which two edge channels areformed at zero field, crossing the magnetic exchange gap. The breaking of TRScan be achieved by magnetic doping of the TI with transition metal or rareearth ions, modulation doping to keep the electronically active channelimpurity free, or by proximity coupling to a magnetically ordered layer orsubstrate, in heterostructures or superlattices. We review the challenges theseapproaches are facing in the famous 3D TI (Sb,Bi)$_2$(Se,Te)$_3$ family, andtry to answer the question whether these materials can live up to the hypesurrounding them.

Magnetic Order in 3D Topological Insulators -- Wishful Thinking or Gateway to Emergent Quantum Effects?