Onions are edible bulbs of plants in the genus Allium, used as a foundational aromatic in cuisines worldwide. Believed to have originated in Central Asia, they have been cultivated for thousands of years and are grown commercially across the globe today, with China, India, the United States, and Iran among the largest producers. Cutting or crushing an onion ruptures its cells and releases volatile sulfur compounds, producing its characteristic pungent flavor and its well-known eye-irritating effect; cooking mellows this pungency into sweetness through caramelization. Milder varieties such as shallots and pearl onions tend toward sweetness, while red and yellow onions are more assertive raw. Onions form the aromatic base of dishes worldwide: French mirepoix, Indian curry bases, and Middle Eastern and Mediterranean braises rely on cooked onion for depth, while raw onion adds crunch and bite to salads, sandwiches, and tacos.