Non-coding RNAs (ncRNAs) play regulatory roles at all stages of the genetic information transmission from DNA to proteins. The ncRNA-mediated mechanisms leading to specific expression or silencing of particular genes seem to be of special importance. In addition to well-known and well-understood functions of RNAs, we recently discover new and nonobvious aspects and possibilities of regulating cellular processes. One example is the processing of various RNAs, the mechanism of formation of short non-coding RNAs from existing functional RNAs. Both: the sources of these short RNAs and the functions performed by them are diverse. Their presence greatly enriches the possibilities of gene expression regulation, as it turns out, at all stages.