Membrane proteins with seven transmembrane helices (7TM) are found in all kingdoms of life. They are mainly involved in signaling (G-protein coupled receptors, GPCRs) but, in case of the retinal-binding subgroup, also include light-driven ion pumps or light-gated ion channels. It is intriguing to see how evolutionarily distinct proteins fulfill different roles based on an apparently similar molecular architecture. The microbial rhodopsin field has seen great progress in the past years. The unexpected discovery of the proteorhodopsin family from marine bacteria showed that type I retinal-binding proteins are more common in nature than originally thought. The other important development was the discovery of the channelrhodopsins, which are light-gated cation channels. The study of channelrhodopsins, primarily in Frankfurt, has given rise to the new field of optogenetics. So far, X-ray structures of ten different microbial rhodopsins have been determined. It still has to be seen what defines their function as sensor, channel, or pump, and how their photocycle kinetics are linked to their conformational dynamics.