And this filtering process takes place in lymph nodes. So along many parts of our lymphatic system are small masses of tissue called lymph nodes. So this is one lymph node, a second lymph node, a third lymph node. And we have many of these lymph nodes along different regions of our body. Now, within these lymph nodes, we have cavities, we have sinuses. And within these cavities, we have specialized types of leukocides wide blood cells.