Rhodopsin (RHO) is a G-protein-coupled photoreceptor essential for vision at low light intensities 1 and required for photoreceptor cell viability after birth 2. The protein functions as a molecular switch in phototransduction: light-induced isomerization of its 11-cis-retinal chr3 to all-trans-retinal triggers a conformational change that activates G-protein signaling 3. This activation is terminated through receptor phosphorylation, which displaces the G-protein alpha subunit via the arrestin SAG 4. Mutations in RHO cause two major inherited retinal dystrophies: retinitis pigmentosa 4, characterized by progressive photoreceptor degeneration, and autosomal dominant congenital stationary night blindness 1, causing severe low-light vision defects. These disease associations underscore RHO's critical role in maintaining normal phototransduction and photoreceptor survival. RHO represents a prototypical example of how G-protein-coupled receptors translate light signals into electrical responses essential for vision.