3’-β-C-Ethynyl-5-methyl uridine is a thymidine analog. Analogs of this series have insertional activity towards replicated DNA. They can be used to label cells and track DNA synthesis. 3’-β-C-Ethynyl-5-methyl uridine is a click chemistry reagent, it contains an Alkyne group and can undergo copper-catalyzed azide-alkyne cycloaddition (CuAAc) with molecules containing Azide groups.