And so we can study the absorption of light when that colored product is produced. And that will give us information as to what happens in that reaction when we use climate trypsin. So, once again, to monitor the reaction progress, we generally use a substrate that changes color when it reacts with the active side. So we have this special substrate molecule that when reacts with the serene inside the active side, it produces a product that has a certain color to it. And we can essentially monitor the color change and the absorbance of light as we produce that particular product. So if we take a look at the following graph the y axis is the absorbance of light of that product produced when the substrate is catalyzed by the active side and the x axis is basically the reaction progress.