A homunculus is a "little man." In the 17th century, theorists called preformationists argued that a human being begins life as a tiny, preformed person — a homunculus — encapsulated in the sperm or, as some thought, in the egg.
The preformationists were arguing against Aristotle's view that humans and other organisms begin life as unformed material that gradually takes shape, and, in the case of humans, this process includes a moment of "ensoulment" — when the embryo gets a soul and becomes fully human. A homunculus can also be a "little man" of any sort. You can describe your Ken doll as a homunculus. The word is the diminutive of the Latin word homo "man."