What parts of a nebula contain the most matter?

The densest parts of a nebula, known as molecular clouds, contain the most matter. These regions are composed of gas and dust that are cooler and more concentrated than the surrounding areas. Within molecular clouds, areas of high density can lead to the formation of stars, as gravity pulls together the material to create stellar bodies. Overall, the core regions of these clouds are where the majority of the nebula's mass resides.