Emission line galaxies are galaxies that exhibit strong emission lines in their spectra, typically arising from the ionization of gas within the galaxy. These emission lines can be produced by a variety of processes, such as star formation, active galactic nuclei, or shocks. By studying the emission lines in galaxies, researchers can learn more about the physical properties and dynamics of the gas within the galaxy, as well as the processes driving the emission. This research area can provide valuable insights into the formation and evolution of galaxies, as well as the underlying astrophysical processes that shape the universe.