Now, initially, what happens to our percentage of those molecules that exist in their double helix form? Well, initially the slope is essentially flat. So what that means, the slope is essentially zero. And initially, changing the PH doesn't really change the amount of DNA molecules that exist in their double helix form. But as we approach a PH of nine, what we see happen is the slope becomes much more steep and much more negative. And so what that means is between the nine and ten PH values, a small change in the PH in the x value creates a very large change in the y value.