In this chapter, you saw the basics of the grammar of graphics as implemented in ggplot2 and how the concept of layer is used in the process of building the graph. You saw the high-level components of a plot such as the scales, coordinate system, and faceting, and you went through some examples of these functionalities. You then explored the concept of layer by reading descriptions of the different components of a layer. In the examples shown, you had the chance to see the basic use of the ggplot() function, which will be the basis for building more advanced examples.