Metabolic labeling of nucleic acids provides a useful tool for life sciences research to get a better understanding of specific cell biology, tissue development and regeneration and other significant biological outcomes. Labelling of nucleic acid is achieved by chemically modified nucleosides or nucleoside analogues. The bioorthogonal modification is used as a marker to provide the binding of a reporter molecule. The analogues undergo endogenous, enzymatically conversion into the nucleoside triphosphate and thus can be integrated by DNA- or RNA- polymerases into nascent nucleic acids. Afterwards the label can be detected over fluorescent reporter molecules. This can make it possible to visualize DNA and RNA in real time in a well-preserved cell structure or even in tissue, to study their biological function.