| Summary: | Na<sup>+</sup> plays a vital role in numerous physiological processes across humans and animals, necessitating a comprehensive understanding of Na<sup>+</sup> transmembrane transport. Among the various Na<sup>+</sup> pumps and channels, light-driven Na<sup>+</sup>-pumping rhodopsin (NaR) has emerged as a noteworthy model in this field. This review offers a concise overview of the structural and functional studies conducted on NaR, encompassing ground/intermediate-state structures and photocycle kinetics. The primary focus lies in addressing key inquiries: (1) unraveling the translocation pathway of Na<sup>+</sup>; (2) examining the role of structural changes within the photocycle, particularly in the O state, in facilitating Na<sup>+</sup> transport; and (3) investigating the timing of Na<sup>+</sup> uptake/release. By delving into these unresolved issues and existing debates, this review aims to shed light on the future direction of Na<sup>+</sup> pump research.
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