A nebula is usually made up of hydrogen gas and plasma. It is the first stage of a star’s cycle. There are four different types of nebula. These are; Emission, Reflection, Dark, and Planetary. Opinions on the number of Nebulae do vary, however, and some of these other types include Planetary and Bright nebula. In the past Galaxies and Star Clusters were also thought to be certain types of nebulae.