Chemically and enzymatically synthesized glycans and glycoconjugates can serve as molecular tools (molecular imaging probes) for investigating glycan functions. However, native glycan structures are susceptible to degradation by glycoside hydrolases, leading to a gradual loss of their biological functions of original glycans or probes (Fig. 27.1a). Additionally, the influence of metabolic byproducts cannot be ignored when interpreting observed biological phenomena. Therefore, the development of glycoside hydrolase-resistant glycan analogs is highly attractive not only as molecular tools but also as potential lead compounds for drug discovery (Fig. 27.1b). When such degradation-resistant glycans are fluorescently labeled, their original structure can be maintained within cells or living organisms regardless of the labeling site. This enables the analysis of the intrinsic localization and behavior of the target glycan. Imaging studies based on this approach provide essential insights that cannot be obtained by other methods; however, they remain largely unrealized due to the difficulty in developing suitable glycan analogs.