Compound microscope was first used to observe cells.
Step-by-step explanation:
In 1965, Robert Hooke observed a slice of cork under a compound microscope and saw the compartments in it. He named these compartments as cell.
The compound microscope has a high magnification power. It uses two convex lenses of short focal length. These lenses are objective lenses and eyepiece. It has resolution of 10X, 40X to obtain a magnified image of tiny entities like cell.