Onions are a spicy vegetable known to humanity for at least five centuries. During this time, people have come to know numerous species, subspecies, groups, subgroups, and cultivars, united by a very similar aroma and taste. Among them are beautiful ornamental plants unlike the familiar onion. Scientists estimate that there are between 400 and 600 plants in the genus Allium, only 18 of which are used as food. How much more can we learn about the varieties of the vegetable commonly known as "onions"? The materials in this section will explore the expanding range, composition, and beneficial properties of various types of this pungent vegetable.