"The Most Important Image Ever Taken"
In 2004, NASA astronomers pointed the Hubble telescope to an area southwest of Orion, focusing on a seemingly empty area equivalent of a 1mm x 1mm square of paper held at 1 meter away. With an incredible exposure time of 11 days, what returned was the image above, the specks of light amounting to over 10,000 galaxies, known as the "Hubble Ultra Deep Field."
Up until a more refined version of this image (known as eXtreme Deep Field) was produced, Ultra Deep Field was the deepest photograph of the heavens in existence, often referred to as "the most important image ever taken" by astronomers and scientists alike.
The sheer scales of distance, time and quantity behind this image are staggering; fortunately this YouTube video from Deep Astronomy helps put things in perspective.