Molecular photoswitches change their geometry and electronic properties due to light stimuli in a reversible fashion. Over the past decades, a wide range of photoswitches has been established. The most prominent ones are stilbenes, azobenzenes, and diarylethenes, which are highly developed and applied in virtually every chemical field. More recent representatives are hydrazones, Stenhouse dyes, imidazole-biradicals, hemipiperazines, peri-aryloxyquinones, or indigoids broadening significantly the structural space, properties, and possibilities for applications. Additionally, the strategic alteration of more classical photoswitch structures also allows for significant leaps in performance and applications, which is well illustrated by the elaboration of azobenzene structures by e.g. introduction of heterocycles, bridging, London-dispersion forces, or halogenation. Since Masahiro Irie pioneered symmetric thiophene substituted diarylethenes (Figure ), research on photochromic diarylethenes undergoing reversible photocyclization between an open isomer and a conjugated closed-ring isomer, has rapidly been growing. An important step forward was the development of synthetic accesses for non-symmetric substituted diarylethenes. Especially the sequential coupling of different aryl groups to a bridgeprecursor allows for more complex structural alterations, which was also crucial for this work (Figure ). Most recently, aza-diarylethenes have been developed in which carbon-carbon bond connections are replaced by carbon-nitrogen connections. This structural elaboration opens up an entire new structure and property space expanding the versatility and applicability of diarylethenes. Aza-diarylethenes developed by the group of Kobatake adhere to classical electrocyclic photoreactivity, leading to carbon-nitrogen single bond formation (Figure ). The aza-diarylethene from our group shows an unusual carbon-nitrogen double bond formation under aromatization while at the same time a zwitterion is obtained via opening of the thiophene ring (Figure ). This zwitterion could further be isomerized between a Z and an E isomeric structure, which established an intrinsic three-state switching behavior. So far however, only the zwitterion-forming reaction was photoresponsive, while the reverse reaction back to the starting state proceeded thermally activated and could not be triggered by light irradiation.