What you are seeing in all these examples is dark material blocking the light from stars and gas behind it. The composition of the material itself remained a mystery for a long time. What that means is that the dust is a complex collection of different types of materials, most of which is actually rather common here on Earth. The particles of dust are not little spheres, though, they form long chains and clumps. But there's a lot of them.
Dust is everywhere.
It's in our solar system, in our Galaxy, between galaxies. It's also a very good absorber of visible light, which is why it's so easy to see against a bright background. Because our Galaxy is so filled with this stuff, we can only see so far before our view is blocked. It's like looking through a smoke-filled room . But now we have a better grasp of its true size, and the fact that we are about halfway to the edge of our vast spiral metropolis .