Why were some of William Harvey’s studies of embryos limited by the lack of microscopes?

While William Harvey made significant contributions to the study of embryology and reproduction, his research was constrained by the technological limitations of his era. Although he produced a wealth of observational detail regarding the development of animals—such as his work on chickens and deer—he was unable to resolve fundamental questions about the process, specifically the roles of sperm and menstrual blood in the formation of the embryo.1

These complex biological matters could not be properly investigated or understood without the use of a microscope, which would have allowed for the observation of microscopic structures and cellular processes that were invisible to the naked eye. While the compound microscope had been invented in the late 16th century, its utility in biological sciences was not realized until the mid-to-late 17th century, after Harvey had already conducted much of his foundational work. Consequently, despite his excellent observational skills, Harvey lacked the necessary tools to peer into the cellular level of embryonic development.123