In this video, we're going to begin our lesson on endocytosis and exocytosis. Up until this point in our course, we've been talking about the membrane transport of very small molecules. But what about large molecules? How do they get across a cell's plasma membrane? Well, large biomolecules, for example, large proteins, large carbohydrates, or nucleic acids like DNA, are simply just way too large to diffuse through membranes or even through protein channels. They are not able to diffuse through the methods that we've talked about so far. Instead, large macromolecules are transported across cell membranes via either the process of endocytosis or the process of exocytosis. We'll get to talk a lot more about endocytosis and exocytosis as we move forward in our course. But down below here, we're showing you a map, a little snippet of our map of the lesson on membrane transport, and notice that we're focusing on bulk transport or the transport of very large molecules. These large molecules can either be transported via endocytosis to enter the cell or exocytosis to exit the cell. We're going to start off our lesson by focusing on endocytosis, entering the cell. There are 3 types of endocytosis that we're briefly going to touch on, which are phagocytosis, cell eating; pinocytosis, cell drinking; and receptor-mediated endocytosis, which is a form of pinocytosis. After we talk about endocytosis, we'll discuss exocytosis, exiting the cell. But for now, this here concludes our introduction to endocytosis and exocytosis, and we'll get to learn more about these processes as we move forward in our course. So I'll see you all in our next video.