Lemon zest is the oil rich outer skin of a lemon. The volatile oils in the zest make it extremely flavorful, which is why some recipes call for the addition of lemon zest in addition to lemon juice or lemon essence. The process of removing lemon zest is known as â€œzesting,â€� and many kitchen supply stores sell tools which are specifically designed to remove lemon zest. Other citrus fruits can be zested as well for an infusion of intense flavor in a wide range of dishes. The peel of a citrus fruit contains two top layers; the zest, and the pith. The zest is shiny, brightly colored, and textured; it is the outer surface of the fruit which consumers can directly see. The pith is a white, fibrous membrane directly below the zest which helps to protect the fruit inside. While the pith of a citrus fruit is often edible, it is not very exciting, so when a fruit is zested, the zest is gently separated from the pith to isolate the flavor.