Do eggs start developing the day they are laid or when put into an incubator?

Eggs start developing the day they are laid.

Here's why:

* Fertilization: A hen's egg is fertilized internally, meaning the sperm meets the egg inside the hen's body.

* Development Begins: Once fertilized, the egg starts developing immediately, with cell division and growth happening even while the egg is still inside the hen.

* Incubation: The incubator only provides the controlled environment (temperature, humidity) needed for continued development.

Essentially, the incubator helps the egg "finish" the development process that was already in progress. It's not the incubator that starts the development, but rather the hen's body and the fertilization that happens before laying.