The soils on the Left Bank of Bordeaux are predominantly gravel based in the best terroirs, which include Médoc, Margaux, Pessac-Léognan, and Pauillac. Of course the soils are not only created from gravel, the various types and sizes of stones resting on beds ranging from limestone, to clay, to sandstone, and other mineral and organic materials play an important role. The gravel soils allow excellent drainage, encourage the roots to burrow deep, help by reflecting sunshine, and radiate heat (which helps the grapes to fully ripen).