eXtreme Deep Field. Source
On September 25, 2012, this photo was released. Called the eXtreme Deep Field, this photo is the culmination of 10 years of observation of one small, empty-looking patch of sky. These Deep Field photos have become iconic, and now scientists are planning to make more of them. A new project is in the works to take 6 more of these photos from other unexplored regions of sky that look empty. Hopefully we will discover that these blank patches of sky aren't actually blank after all.
I recommend reading this article to learn more.