Fluorophores and haptens, are the most commonly used labels for the generation of non-radioactive RNA/cRNA probes. They are enzymatically introduced into RNA/cRNA via modified nucleotides that are incorporated as substitutes for their natural counterparts in either a one-step procedure (introduction of a fluorescent or hapten-modified nucleotide) or a two-step procedure (introduction of a reactive group carrying nucleotide and subsequent fluorescent or hapten labeling).
| Label | Labeling Kits | Single Nucleotides |
| Fluorophore | Fluorescent in vitro Transcription Kits | Fluorescent Nucleotides |
| Hapten | Biotin&Digoxigenin in vitro Transcription Kits | Biotinylated Nucleotides Digoxigenin-/DNP-modified Nucleotides |
| Amine | Amine-modified Nucleotides | |
| CLICK | Copper-free CLICk T7 in vitro Transcription Labeling Kits | CLICK-functionalized Nucleotides |
| Nucleotide dependent |
