Transcript: Astronomers have learned much about galaxies in cosmology by the intensive study of very small regions of sky. By looking with a variety of telescopes at a variety of wavelengths very hard at one region of the sky astronomers can punch through the universe reaching almost the entire span of galaxy and star formation, ten or eleven billion years of look-back time. The most famous of the deep fields have been done by the Hubble Space Telescope which had a northern and a southern deep field and more recently an ultra-deep field. The Hubble Space Telescope stares in the deep field observation for hundreds of orbits in the same tiny patch of sky. The depth reach in these observations is phenomenal, twenty-five magnitudes fainter than the naked eye can see on a dark sky. Twenty-five magnitudes is a factor of ten to the ten, ten billion times fainter than the eye can see. These deep fields have been used to show that galaxies formed relatively early in the universe, about a billion years or so after the big bang.