Did you know that you can see into an egg before it hatches without breaking it open? Using a process called candling, you can see the outline of blood vessels, the chick's body, and the air cell. Here are some resources to help you learn about candling.

Inside the Egg: Hatching Chickens
This is a Utah Agriculture in the Classroom lesson plan that explores the hatching cycle of an egg and explains how to build a home-made egg candler out of basic materials.

The inside of the egg will change as the chick grows and prepares to hatch. The air cell grows larger, the blood vessels join the chicks body and eventually disappear, and the movement that begins around day 9 will begin to slow down around day 18. Here are some videos of what you are likely to see when candling fertile eggs.

Note: White eggs will be easier to see into while colorful and brown eggs will likely be more difficult or even impossible to see into.

Day 4 (Still image; the heart begins to beat on day two, but it is likely to be visible and regular by day 4)
external image Candled+Polish+Egg+6-18-12.jpg

Day 7 (Video - the chick moves inside the egg)

Day 13 (Video - the chick moves even more)

Starting around day 18 and going until it hatches, the chick will be so large inside the egg you will not be able to see much movement. However, as the chick prepares to hatch on day 20 you will be able to hear chirps from inside the egg. If you candle at this point, you will be able to see the chicks head poking up into the air cell which means he is now breathing air. This indicates the chick is preparing to hatch.

Day 20 (Video - chick is peeping, head visible in air cell space)