Nebular emission is a research area that focuses on studying the emission of light from nebulae, which are large clouds of gas and dust in space. These emissions can come from a variety of sources, such as ionized gases, dust particles, and the radiation of hot stars within the nebula. Researchers in this field study the different types of emissions, their origins, and the physical conditions within the nebula that give rise to them. This research can provide valuable insights into the evolution of stars, galaxies, and the interstellar medium.