This chapter describes the lattice package, developed by Deepayan Sarkar[54]. Lattice is based on the grid graphics system, but can be used as a complete graphics system in itself and a great deal can be achieved without encountering any of the underlying grid concepts.∗ This chapter deals with lattice as a self-contained system consisting of functions for producing complete plots, functions for controlling the appearance of the plots, and functions for opening and closing devices. Section 5.8 and Section 6.7 describe some of the benefits that can be gained from viewing lattice plots as grid output and dealing directly with the grid concepts and objects that underly the lattice system.