Mustard seeds are the small round seeds of various mustard plants. These seeds usually derive from one the following plants; black mustard (Brassica nigra), white mustard (B. hirta/Sinapis alba) or brown Indian mustard (B. junca). Mustard seeds are an important ingredient when it comes to spicing foods. The seeds are very small, about 1-2 mm or 0.039 to 0.079 inch) in diameter and vary in colour from yellow/white to black.
To prepare the well-known condiment mustard, the seeds are grinded and mixed with water, vinegar or another liquid.