Thanks to a see-through material and a little ingenuity, we can now see what's happening inside a bird's egg. Scientists from Tsinghua University in Beijing invented a transparent shell made from polydimethylsiloxane, a polymer based on silicon, that mimic the shape and feel of a natural eggshell.
Before this invention, the way scientists could see inside an egg was through "," which is exactly what it sounds like: cutting a tiny hole and peeking inside.
As the university's notes, the researchers developed the transparent egg to act as a vehicle for easier and cheaper biological testing. The side benefit is an amazing view like this: