Damn, science. Researchers at Tsinghua University in Beijing, China have created a see through eggshell to keep track of how an embryo grows over time. The material is made from a soft, silicon-based organic polymer that maintains the shape of a real eggshell but is completely transparent.
When I first saw this x-ray photo I thought it was some frame from a sci-fi movie but I was wrong. It's actually the embryo of a bat, from the Society Française de Biologie
This is the oldest embryo ever discovered on Earth, found in Uruguay and Brazil. It is a baby mesosaur, a group of small aquatic reptiles from the early Permian. According to the researchers, it's the earliest known case of viviparity.