Can we somehow create a eukaryotic gene that does not contain these intro sections, these intron sections here? Because if we can somehow create a Eukaryotic gene, if we somehow can take this Eukaryotic DNA and remove these introns just simply splice together the blue sections, then we'll form a gene that doesn't contain these useless intron sections. And then we take that gene, place it into that bacterial cell, and that bacterial cell won't have to worry about removing these introns, and so it can easily form that eukaryotic protein. So this is called building a complementary DNA library. So a complementary cDNA library is a library that consists of eukaryotic genes in which we have removed all these different introns. So to see how we can build a cDNA library, let's take a look at the following five steps.