The studies conducted during the last decade revealed that RNA molecules play much more different roles in the living world than it had been expected earlier. They can function in biological systems as: carriers of genetic information, enzymes, cofactors inducing or mediating biochemical reactions, inhibitors which deactivate enzymes or agents that regulate cellular processes. Consequently, several new RNA-based methods and techniques have been elaborated. They permit to identify RNA molecules that display some specific properties, selectively induce gene silencing or gene expression in bacterial, plant and animal cells. Generally, it is becoming increasingly apparent that RNA-based technologies should be considered one of the major factors influencing further development of modern biotechnology.