Celery seeds come from the celery plant and have a similar flavor profile, grassy, a little sweet and a little bitter. In fact, they can used as a substitute for celery in recipes if you don't have any on hand. Be sure to grind the seeds when adding to soup or salad, otherwise toss them whole into any pickle brine.
Grind the seeds and combine with salt to make celery salt, which is a perfect addition to a Bloody Mary cocktail or tomato soup.
Celery seed is thought to be an antioxidant and increase metabolism.