The encapsulation of dyes into the cavity of macrocyclic supramolecular structures leads commonly to an alteration of their photophysical properties, such as their absorption and fluorescence spectrum, fluorescence lifetime, photodecomposition quantum yields and pathways, and so on. This can be used to sound out the microenvironment of macrocyclic cavities. For example, solvatochromic dyes have often been used to determine the hydrophobicity and polarity of the cavity, whereas we have identified a dye to obtain information about the polarizability. Morevover, numerous interesting applications are immediately emerging from this research, which include sensing, live cell imaging, lasing, stabilizing, and others.

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