This review summarizes the structures, functions, and molecular mechanisms of microbial and animal rhodopsins. Rhodopsins are membrane proteins that use light to drive ion transport. The study highlights the conservation of key amino acids in the transmembrane (TM) helices, which are crucial for activity and selectivity. Despite low global sequence identities among microbial rhodopsins, certain residues are conserved in sequence and position, suggesting functional importance. The study also discusses the functional conversion between light-driven proton and chloride pumps, showing that a single amino acid replacement can switch the function of BR to a chloride pump. However, substituting BR-like residues into HR does not result in a functional proton pump, indicating the importance of hydrogen bonding for proton pumping. The study also maps sequence and motif conservation in GPCRs, showing that greater "tube" thickness corresponds to higher residue conservation. The study identifies conserved motifs, such as the (D/E)RY motif in TM3 and the NPxxY(x)F motif in TM7 and H8. The inverse agonist 11-cis retinal is attached to Lys296, and certain residues act as microswitches for stabilizing the active receptor state. The study provides insights into the molecular mechanisms underlying the diverse functions of rhodopsins.This review summarizes the structures, functions, and molecular mechanisms of microbial and animal rhodopsins. Rhodopsins are membrane proteins that use light to drive ion transport. The study highlights the conservation of key amino acids in the transmembrane (TM) helices, which are crucial for activity and selectivity. Despite low global sequence identities among microbial rhodopsins, certain residues are conserved in sequence and position, suggesting functional importance. The study also discusses the functional conversion between light-driven proton and chloride pumps, showing that a single amino acid replacement can switch the function of BR to a chloride pump. However, substituting BR-like residues into HR does not result in a functional proton pump, indicating the importance of hydrogen bonding for proton pumping. The study also maps sequence and motif conservation in GPCRs, showing that greater "tube" thickness corresponds to higher residue conservation. The study identifies conserved motifs, such as the (D/E)RY motif in TM3 and the NPxxY(x)F motif in TM7 and H8. The inverse agonist 11-cis retinal is attached to Lys296, and certain residues act as microswitches for stabilizing the active receptor state. The study provides insights into the molecular mechanisms underlying the diverse functions of rhodopsins.