The article by Laura M. Herz discusses the fundamental mechanisms and limits of charge-carrier mobilities in metal halide perovskites (MHPs), which have seen significant advancements in power conversion efficiencies for photovoltaic applications. The high mobility values in MHPs are attributed to their favorable semiconducting properties, such as strong interband transitions and low trap-related recombination rates. However, the intrinsic and extrinsic factors that limit these mobilities are explored, including electron-phonon coupling, grain boundaries, energetic disorder, and self-doping. The intrinsic limits are primarily set by Fröhlich interactions, which are dominant in MHPs due to the polar nature of the lead-halide bond. Extrinsic factors, such as grain size and impurities, can significantly reduce mobilities, particularly in tin-based perovskites. The article also highlights the potential of using cesium substitution to stabilize the crystal structure and improve mobility in FA-based perovskites. Overall, the best solution-processed or evaporated MHP thin films already reach charge-carrier mobilities close to the theoretically achievable limits, demonstrating the remarkable progress in this field.The article by Laura M. Herz discusses the fundamental mechanisms and limits of charge-carrier mobilities in metal halide perovskites (MHPs), which have seen significant advancements in power conversion efficiencies for photovoltaic applications. The high mobility values in MHPs are attributed to their favorable semiconducting properties, such as strong interband transitions and low trap-related recombination rates. However, the intrinsic and extrinsic factors that limit these mobilities are explored, including electron-phonon coupling, grain boundaries, energetic disorder, and self-doping. The intrinsic limits are primarily set by Fröhlich interactions, which are dominant in MHPs due to the polar nature of the lead-halide bond. Extrinsic factors, such as grain size and impurities, can significantly reduce mobilities, particularly in tin-based perovskites. The article also highlights the potential of using cesium substitution to stabilize the crystal structure and improve mobility in FA-based perovskites. Overall, the best solution-processed or evaporated MHP thin films already reach charge-carrier mobilities close to the theoretically achievable limits, demonstrating the remarkable progress in this field.