So I've googled around (even for images!) with the phrase "Start the presses!", in order to find out what it means and what its etymology is. My results are inconclusive. It seems to be used when an important discovery was made, or late breaking important news events unfold, e.g. as in this article in Nature about a new material (with tongue-in-cheeck?)
What does it mean? Who would use it when? When was it first used?