A button mushroom is the young, small form of the common cultivated mushroom, Agaricus bisporus, harvested with its cap still closed around the stem. White, firm, and mild, it is the most widely sold mushroom in Western markets, eaten raw in salads or cooked in countless dishes. As it matures it becomes the larger cup and flat mushrooms, and the same species grown brown is sold as chestnut or cremini. Button mushrooms supply B vitamins, selenium, potassium, and a small amount of vitamin D when exposed to sunlight. Their mild flavour absorbs sauces well, and they brown nicely when seared over high heat.