[en] The interplay of charge, spin and heat transport is investigated in the fascinating research field of spin caloritronics, the marriage of spintronics and thermoelectrics. Here, many new spin-dependent thermal transport phenomena in magnetic nanostructures have been explored in the recent years. One of them is the tunnel magneto-Seebeck (TMS) effect in magnetic tunnel junctions (MTJs) that has large potential for future nanoelectronic devices, such as nanostructured sensors for three-dimensional thermal gradients, or scanning tunneling microscopes driven by temperature differences. The TMS describes the dependence of the MTJ’s thermopower on its magnetic configuration when a thermal gradient is applied. In this review, we highlight the successes from the first observation of the TMS in 2011 to the current ongoing developments in this research area. We emphasize the different heating techniques, material designs, applications and additional physical aspects such as the role of the thermal conductivity of the barrier material. We further demonstrate the efficient interplay between ab initio calculations and experiments within this field, as this has led, e.g. to the detection of large TMS ratios in MTJs with half-metallic Heusler electrodes. (topical review)