A nebula is a cloud of gas and dust in space. It is a celestial object that is often visible in the night sky, especially through telescopes or binoculars. Nebulae are formed from the remnants of dead stars, such as supernovae, or from the gravitational collapse of interstellar gas and dust. Nebulae come in different shapes and sizes, from small, dark globules of gas and dust, to large and bright emission nebulae, such as the Orion Nebula. Some nebulae are also known as reflection nebulae, where the light from nearby stars reflects off the dust and illuminates the gas cloud. Others are known as planetary nebulae, which are formed when a dying star sheds its outer layers and leaves behind a glowing shell of gas. Nebulae are important objects for astronomers as they help us understand the process of star formation and the evolution of galaxies. They are also among the most beautiful and awe-inspiring objects in the universe.