Halide-perovskite semiconductors have a high potential for use in single-junction and tandem solar cells. Despite their unprecedented rise in power conversion efficiencies (PCEs) for photovoltaic (PV) applications, it remains unclear whether perovskite solar modules can reach a sufficient operational lifetime. In order to make perovskite solar cells (PSCs) commercially viable, a fundamental understanding of the relationship between their nanostructure, optoelectronic properties, device efficiency, and long-term operational stability/reliability needs to be established. In this review, the phase instabilities in state-of-the-art formamidinium (FA)-rich perovskite absorbers is discussed. Furhermore, the concerted efforts are summarized in this prospect, covering aspects from fundamental research to device engineering. Subsequently, a critical analysis of the dictating impact of the nanoscale landscape of perovskite materials on their resulting intrinsic stability is provided '. Finally, the remaining challenges in the field are assessed and future research directions are proposed for improving the operational lifetimes of perovskite devices. It is believed that these approaches, which bridge nanoscale structural properties to working solar cell devices, will be critical to assessing the realization of a bankable PSC product.