You're inputting into one function, then taking that output and inputting it into another. So you could have a function u here, which takes the square root of whatever it's input in, is. So u of x is equal to the square root of x. And then you take another, and then you take that output and input it into another function that we could call v. And what does v do? Well, it takes the natural log of whatever the input is. In this case, in the case of f, or in the case of how I've just diagrammed it, v is taking the natural log, the input happens to be square root of x. So it outputs the natural log of the square root of x.