Malpighi, professor of medicine and personal physician to Pope Innocent XII, continued the work of his countryman Andrea Cesalpino by classifying forms of life on a graded scale. Drawing on the work of William Harvey, he studied the circulatory and respiratory systems of all living things and arranged them in a hierarchical system, beginning with plants, above which were insects, then fishes, then the mammals, then man.
Because of his important work on anatomy and embryology, including pioneering use of the microscope, a number of anatomical structures still bear his name: Malpighian corpuscles in the circulatory and lymphatic systems, the Malpighian layer of the epidermis, and the Malpighian tube in insects. He was one of the first scientists to study such anatomical structures as the lungs, kidneys, spleen, brain, tongue, and skin at the microscopic level.