How does the zebrafish's external embryo development compare to mammals regarding studies on embryogenesis?

It provides a unique, non-invasive window unavailable with internal development.

The manner in which zebrafish development occurs offers a distinct advantage over mammalian models like the mouse when focusing on embryogenesis and vascular growth. Zebrafish exhibit external embryo development, meaning the entire process occurs outside the mother's body. This, coupled with the transparency of the embryos, grants scientists a unique, non-invasive window into early life processes, allowing for direct visualization of organ formation and function. Mammals, conversely, undergo internal development, which severely restricts or complicates direct, real-time, non-invasive observation of these fundamental developmental milestones.