Question

When RNAi and micro RNAs became part of the same system, and how was it discovered?

Answer 1

well the process of combining the two didn't happen in the laboratory, but in the heads of the scientists. you see:

RNA interference is based on the interaction of small RNA molecules with the DNA. The same goes for micro RNA mechanisms.#

as for the discovery process: http://en.wikipedia.org/wiki/RNA_interference#History_and_discovery