And we'll talk about the function of these cells in just a moment. So let's take a look at our filtration layer. So if we take a cross section, if we look at this section here, we get the following diagram. So, as the blood travels through the blood capillaries of the glomerulus, we basically have a layer of different cells known as our filtration membrane. So this is a three layer membrane. So these rest cells are the endothelial cells of the blood vessels that contain the tiny pores, the tiny holes that allow the movement of small molecules, such as water molecules, amino acids, glucose molecules, as well as electrolytes, such as sodium ions, potassium ions, and other things.