And during our purification process, when we're isolating that specific protein we can use the specific activity value to basically determine how pure our sample actually is. So we conduct our protein acid and we know that the protein is found inside our sample. And then we begin carrying out the purification processes. And during these processes, this is when we use the specific activity value, as we'll see in just a moment. So in the next lecture, we're going to focus on the different types of processes that we can use to basically purify our sample. In this lecture, we're going to focus on measuring enzyme activity.