And let me draw one of those infinitely thin rectangles, maybe not so infinitely thin. So let me draw it like this. So that would be one of the rectangles. That would be another rectangle. This should be reminiscent of a Riemann sum. In fact, that's where the Riemann integral comes from, taking a Riemann sum where you have an infinite number of these rectangles where the width of each of the rectangles, this is how I conceptualize it, is dx. And the height of this rectangle is the function evaluated at an x that's within this interval right over here.