And we'll discuss how this actually takes place in the next several lectures. So this is a brief introduction to different types of white blood cells found inside our immune system. We also actually have other types of white blood cells. For example, we have mass cells and we have dendritic cells and we're going to focus on these in the next several lectures. So once again, we have three different types of categories of leukocytes. We have granulocytes, a granulocytes and megacariocytes.