For example, we have the nuclei, we have dorogynalle such as mitochondria, we have the ribosomes and so forth, all these different things mixed in inside our test tube. And this is called a homogeneous. Now once we form the homogeneous, we now expose the homogeneous to a process known as differential centrifugation and we conduct several centrifugation processes as we'll see in just a moment. Now, if you don't know what differential centrifugation is, we're going to focus on the details of that process in the next lecture. But what it basically does is it uses angular motion, it uses centripetal acceleration to basically separate the components inside the homogeneous based on their density. So the more dense a certain component is, the lower along our test tube it will end up and the less density is, the higher up along a test tube it will actually be.