So inside our body we have the process we call the blood clot cascade. And what this basically involves is the proteolytic activation of many different types of zymogens into many different types of active enzymes which basically help us produce those proteins which are involved in creating the clog, when, for example, there's some type of trauma to blood vessel inside our body. So when we experience trauma or some type of cut to the blood vessels, our body initiates a response that involves a cascade of proteolytic cleavages that ultimately produces enzymes and proteins which are responsible for basically sealing off that cut in that trauma area. Now, one example that we're going to look at in the next several electrodes is prothrombin. This is a very important zymogen that is activated into the thrombin which basically needed to produce those fibrin molecules that essentially form that clock. Now let's discuss three, four, five and six.