Comparative embryology is the study of how different types of organisms compare to one another during their fetal stages. The Greek philosopher Aristotle is considered the world's first recorded comparative embryologist, in that he was the first to publicly acknowledge that certain types of animals were born from eggs while others gave birth to live young.
Modern Comparative Embryology
During the modern age, scientists have used comparative embryology to study and gather evidence of evolution, which can be traced back to the work of Karl Ernst von Baer and Oscar Hertwig in the 1800s. Today, scientists study comparative embryology to better understand the reproductive cycles of all manners of animal life, and for practical reasons as well as simply to further human understanding. For example, marine biologists use highly advanced microscopes and time-lapse video to better understand the fertilization of marine embryos, gametes and larvae.