Learn: Many religions, including Christianity, Buddhism, and Islam, contain parables about these tiny, perfectly spherical seeds, which are found tucked inside the seed pods of the mustard plant, a cruciferous cousin to broccoli and cabbage. Although there are more than 40 varieties of the plant, only two are commonly harvested for their seeds. One produces pungent brown seeds, which have a sharp, spicy-hot flavor and are used in Dijon mustards; the other yields milder, yellowish-white seeds used to make traditional American mustard.
Purchase: Since the mustard plant is grown all over the world, seeds of both colors are widely available. Look for them in the spice aisle of your market. (You also may find ground or powdered mustard seeds.)
Use: The seeds' spiciness makes them choice additions to rubs and seasonings. They're also used for pickling. For another use, gently toast them for a few minutes in a dry skillet, shaking the pan frequently to avoid burning. The seeds will develop a nutty essence and crunch that makes a nice garnish for fish, salads, and rice.
Store: Mustard seeds will keep in a tightly sealed container stored in a cool, dark place for up to one year.