The Interstellar Medium and Protostars

When we look up into the night sky we see stars, and not much else. So we get the impression that between the stars, space is empty. There doesn’t seem to be any sort of material that lies between one star and another. At the same time, we know intuitively that this cannot be true, for if space were empty, from what did stars form? This then leads us to the conclusion that perhaps space is not quite so empty, but filled with some sort of material that, to our eyes, is all but invisible yet is responsible for providing the source material for stars.