I use this page at the beginning of my chick hatching unit. I bring the eggs and put in the incubator for the kids. I then read a few books on eggs.
An Egg is Quiet, Who's in This Egg, An Extraordinary Egg.
Then I have the kids guess what is going to be in the egg. Every guess is acceptable. On the What's inside? page kids draw what they think will be inside and label it. Use the other page for the kids to just cut out the egg and then glue just the top of the egg to the What's inside page. Hang these up on a bulletin board with a big picture of the eggs in the incubator. Everyone loves to lift the flap and see what my Kindergarten students think will be inside the eggs. After that we learn about eggs and the animals that hatch out of them.