As previously mentioned, photopharmacology relies on the use of molecular photoswitches being incorporated into the structure of biologically active molecules which allows their potency to be controlled optically. They are introduced into the structure of bioactive compounds via insertion, extension, or bioisosteric replacement. These incorporations can be supported by structural considerations of the molecule or SAR (structure-activity relationship) analysis to determine the optimal position. Some examples of photoswitchable molecules commonly used in photopharmacology are azobenzenes, diarylethenes, and photocages.