Aluminum (Al) alloys, a typical lightweight material, are limited to applications at temperatures below about 200 ^oC. The high-temperature range of 300-400 ^oC has been a longstanding bottleneck for traditional Al alloys. In this study, the underlying mechanisms of this service bottleneck are first discussed, and key scientific solutions aimed at overcoming the bottleneck are proposed. A new microstructure designing strategy is proposed to develop advanced heat-resistant Al alloys through phase transformation that couples rapidly diffusing solute atoms with slowly diffusing ones. This strategy leads to three design approaches for thermal stability: (1) interfacial solute segregation at the nanoprecipitate/matrix interfaces, (2) interstitial solute ordering within the coherent nanoprecipitates, and (3) multiple interfacial coherency coupling with multiscale microstructural features. By manipulating the microalloying effect at the atomic length scale, a series of 300-400 ^oC heat-resistant Al alloys were developed. Furthermore, the potential development directions of the heat-resistant Al alloys are also explored as possible references for future work.