Aristotle was the earliest person in recorded history to study embryos.
Many erroneous theories were formed in the early years of comparative embryology.
For example, German biologist and philosopher Ernst Haeckel proposed that all organisms went through a "re-run" of evolution he said that 'ontogeny repeats phylogeny' while in development.
The field of comparative embryology aims to understand how embryos develop, and to research the inter-relatedness of animals.
It has bolstered evolutionary theory by demonstrating that all vertebrates develop similarly and have a putative common ancestor.