Using Prepositional Phrases
A preposition shows position or direction. Common prepositions include above, after, around, beside, by, into, of, over, and with.
I placed a drop of isotonic solution on the microscope slide.
A prepositional phrase starts with a preposition, contains an object (a noun or pronoun), and includes any words that modify the object.
Then I slid the slide under the optical microscope.