So once the information is passed down transduced across the cell membrane to one step two takes place, the cell reacts by increasing the production of some sort of intracellular molecule called a secondary messenger. So, for instance, one example of a secondary messenger is cyclic adenosine monophosphate. Another example of is a calcium. And we have many other examples that we're going to look at. Now, the important part about step three is it creates an amplification of that signal. Why and what is that?