Once upon a time, there was a very special camera called the Hubble Space Telescope. It was put up in space by some very smart people who wanted to learn more about the universe.
One day, this special camera was pointed at a small spot of the sky that was dark and didn't have any stars that we can see from Earth.
The camera took a picture of that spot for many days and nights, and when it was all done, a beautiful picture was taken.
This picture showed us millions of stars and galaxies that were very far away from us, and we had never seen them before. We called this picture the Hubble Deep Field, and it helped us learn a lot about the universe we live in.
So, the Hubble Deep Field is a picture taken by a special camera, showing us stars and galaxies that were very far away and we had never seen before. It helped us learn more about the universe.