Every single eukaryotic cell contains the nucleus. The nucleus is a membrane enclosed organelle that contains, stores, protects and expresses most of the genetic information that is found in our cell, the DNA, the deoxyribonucleic acid. The reason I say most and not all is because actually a small portion, a small portion of the DNA is found in the mitochondria, which is another membrane enclosed organelle found in our body. And we'll discuss that when we look at the mitochondria in its structure. In this lecture, we're going to focus on the structure and the composition of the nucleus, of the eukaryotic cell. So let's begin by discussing the envelope, the region that basically encloses our nucleus.