**3. Conclusion**

CyDs are a versatile tool in the molecular recognition and sensing. Formation of inclusion complex cause to some spectral changes which have been used successfully for the study of host-guest interactions. Additionally the desired spectral changes as the results of complex formation have been used for promote analyte detection and continue to inspire creative applications. The most sensible spectral changes were reported for chemical and fluorescence indicators. These considerable changes have been used for the study and better detection of many absorbing and especially fluorescent species. Moreover many spectrochemically silent organic and some inorganic compounds cause color/fluorescence change in CyD and indicator solutions, because of their competition to form inclusion complex. These changes cause to recognition of the target competitive hosts. On this basis some "indicator modified cyclodex‐ trin" in which indicator is linked to cyclodextrin via a spacer, was synthesized that change color/fluorescence in response to the presence of molecules, ions and many biologically important compounds. The guest-induced changes that are roughly parallel to its binding constants were used for molecule sensing. These are valuable for qualitative and quantitative chemical analysis. Sensitivity and selectivity improved by appropriate designing of the dye moiety or spacer.
