R in a Nutshell, 2nd Edition

grid

This package is a low-level graphics system that provides a great deal of control and flexibility in the appearance and arrangement of graphical output. It does not provide high-level functions that create complete plots. What it does provide is a basis for developing such high-level functions (e.g., the lattice package), the facilities for customizing and manipulating lattice output, the ability to produce high-level plots or non-statistical images from scratch, and the ability to add sophisticated annotations to the output from base graphics functions (see the gridBase package). For more information, see the help files for grid.