Words like down, in are not always prepositions. Compare:
I ran down the road. He's in his office.
Please sit down You can go in
In the expressions down the road and in his office, down and in are prepositions: they have objects (the road, his office).
In Please sit down and You can go in, down and in have no objects. They are not prepositions, but adverbs of place, which modify the verbs sit and go.
Small adverbs like this are usually called 'adverb particles' or 'adverbial particles'. They include in, out, up, down, on, off, through, past, away, back, across, over, under. Adverb particles often join together with verbs to make two-word verbs, sometimes with completely new meanings. Examples: break down = 'stop working'; put off = 'delay', 'postpone'; work out = 'calculate'; give up = 'stop trying'. For information about these verbs, see the next section.
Benefits of Celery
It helps you calm down
Celery for stressrelief? Oh yes! The minerals in celery, especially magnesium, and the essential oil in it, soothe the nervous system. If you enjoy a celerybased snack in the evening, you will sleep better. Celery herb bears umbelliform flowers at the top of the stalk in the second year. Edible cluster of long, darkgreen, somewhat hollow stalks grow upright from the crown of the plant. Its leaves have similar appearance to that of flatleaf parsley.