And in this lecture, we're going to focus on the most common method of regulating genes in eukaryotic cells, and this is on the level of transcription itself, so by actually changing the rate at which transcription takes place. So in this lecture, we're going to briefly discuss the different components that are found along a eukaryotic gene. So this basically describes a diagram of a basic eukaryotic gene. And we have five important components. We have exxons, we have introns, we have our transcription start site, we have promoters, and we have enhancers. So let's begin by discussing what we mean by exons and introns.