A stellar nebula is a vast cloud of gas and dust in space, often considered the birthplace of stars. These nebulae can be composed of hydrogen, helium, and other ionized gases. Over time, gravity pulls the material together, leading to the formation of new stars and planetary systems. There are different types of stellar nebulae, including emission nebulae, which glow due to ionized gases, and reflection nebulae, which shine by reflecting light from nearby stars. Some famous examples include the Orion Nebula and the Eagle Nebula, both of which are visible from Earth and showcase the beauty of star formation.