And so if we take this DNA molecule and we place it inside a eukaryotic cell, it will be able to use this complementary DNA molecule to synthesize the proteins because it won't have to worry about those introns, because those introns were removed in this process inside the eukaryotic cell. Now, because single stranded DNA molecules are less stable than double stranded DNA molecules, what we have to do is we have to take the single stranded DNA molecule, mix it with DNA polymerase to form the more stable double stranded complementary DNA molecule. Now, this process is done with a single eukaryotic gene, but we can carry out with many different types of genes within that eukaryotic organism. And so at the end, what we end up producing is this library of genes for that particular eukaryotic organism. And inside every single gene, every single DNA molecule, we essentially removed all these introns and only kept the exons. And now if we take any one of the genes within the cDNA library and place it inside the eukaryotic bacterial cell, that bacterial cell will easily be able to take that DNA molecule, the gene create the mRNA molecule that is already fully processed, because the complementary DNA molecule is complementary to that fully processed mRNA molecule.