Mustard seeds are the small round seeds of various mustard plants. The seeds are usually about 1 to 2 millimetres (0.039 to 0.079 in) in diameter and may be colored from yellowish white to black. They are important spice in many regional foods and may come from one of three different plants: black mustard (Brassica nigra), brown Indian mustard (B. juncea), or white mustard (B. hirta/Sinapis alba). Grinding and mixing the seeds with water, vinegar, or other liquids, creates the yellow condiment known as prepared mustard.