It has been widely assumed that, in vivo, all the initiation of RNA transcription occurs using NTPs only, but it was observed recently that one kind of smalls RNA, nanoRNAs, could also serve as primers for transcription initiation. Perhaps a balance exists between nanoRNA-initiated transcription and NTP-initiated transcription, and altering this balance could significantly impact the global gene expression. The phenomenon of nanoRNAs initiation transcription challenged a few of traditional understandings in molecular biology, such as transcriptional initiation，the functional mechanisms of small RNAs and coupling relations between RNA decay and RNA transcription, thips henomenon also provided a new opportunity of deepening the research in molecular biology.