The lemon, Citrus limon, is a species of small evergreen tree in the flowering plant family Rutaceae. Juice from lemons is used for purposes such as cooking, cleaning, and as a fragrance ingredient. Lemon peel oil comes from cold-pressing the lemon peel rather than the inner fruit. In fact, the peel is the most nutrient-dense portion of the lemon because of its fat soluble phytonutrients.