So let's suppose we take this same eukaryotic DNA molecule that contains these introns and these exons. So this is our DNA library shown here. So we have these introns, we have the exons and this is our gene, the eukaryotic gene. So the first step is to allow that eukaryotic cell to transcribe this DNA molecule into the single stranded pre mRNA molecule. And pre simply means it has not yet been processed by that eukaryotic cell. Now, instead of taking out the premrina molecule, let's keep the prem RNA molecule inside that eukaryotic cell.