A graphical display consists of graphical objects drawn on the screen. The relative positions of the graphical objects drawn is crucial: in a scatterplot the point symbol positions display the relationship between two variates while in a scatterplot matrix the panels are positioned so that in each row (column), the vertical (horizontal) variate is held constant with the horizontal (vertical) variate changing from one panel to the next. Layout, then, refers to the task of positioning views relative to each other. Clearly, layout is a key step in organising information graphically.