NGC 604 is a star-forming region about 1500 light-years across at a distance of about 2.7 million light-years away from us. And the Chandra X-ray space telescope took images of the region to discover a wall of hot X-ray emitting gas dividing the region into two. In the left side of the image below, gas is heated up both by the stellar winds from young stars and the supernovas. But in the right side of the image, hot gas is heated up entirely by the stellar winds from 200 massive stars, implying that the current star formation on that side is much more recent, and the wall of gas between the two sides block much of the energy emitted by the supernovas from the left side.
It's just somehow fascinating to see how gas that is about as dense as outer space around our own planet, in other words pretty much a vacuum to us fragile humans, could have a major effect in cosmic terms. Despite how sparse such gas must be, having light-years worth of the stuff does have an impact.