What is the symbolism of the cellar where the children are hidden after the Nazis believe them all to have been killed in the biography, Yellow Star?

The cellar symbolizes rebirth. The children are hidden in the cellar after the Nazis believe all the children in the ghetto have been killed. When the Nazis finally discover the children, they are forced out into the street. Instead of killing the children, the Nazis let them return to their families after the adults make a stand.