Dark nebulae are dense clouds of gas and dust in space that block light from stars and other celestial objects behind them. They are often seen as dark patches against the brighter background of the Milky Way or other galaxies. These regions are crucial for star formation, as they provide the necessary material for new stars to develop. These nebulae can vary in size and shape, with some being small and compact while others stretch over vast areas. Famous examples include the Horsehead Nebula and the Coalsack Nebula. Studying dark nebulae helps astronomers understand the processes of star birth and the structure of our universe.