Ice

As more water molecules stick together with hydrogen bonds, they form a regular pattern, as shown here.  

Simplified diagram of water ice

We see these patterns when we look at snowflakes under a microscope, or see frost on a window pane. The reason these patterns form is that the water molecules have a V shape, and hydrogen bonds form at the ends of these Vs.

As more and more molecules stick a thick layer of sticky ice grows up around each dust grain in the disc of the Galaxy. As well as water ice, many other sticky molecules stick to each dust grain. These molecules are not sticky on Earth, but they were in the cold dust clouds of space. Methane and ammonia both formed ices around dust grains. We can think of the dust grains as forming the center of tiny snowballs.