text: It is the deepest image of the universe ever taken , looking back approximately 13 billion years ( between 400 and 800 million years after the Big Bang ) , and it will be used to search for galaxies that existed at that time .
simplified: It is the deepest image of the universe ever taken by Hubble , looking back ( to when the universe is thought to have been 800 million years old ) approximately 13 billion years ago .