The present invention relates to photo-switchable azobenzene compounds and their uses in the labeling of target proteins and as research tools. The present invention further relates to photo-sensor proteins, comprising a tag and the photo-switchable azobenzene compounds attached to said tag and their uses as research tools. The present invention further relates to the medical use of the photo-switchable azobenzene compounds and/or the photo-sensor proteins in the diagnosis and/or treatment of sight disorders and in the improvement of vision.
