An H II region is a large cloud of gas and dust in space where new stars are forming. These regions are primarily composed of ionized hydrogen, which gives them their name. The intense radiation from young, hot stars within these regions ionizes the surrounding hydrogen gas, causing it to glow brightly. H II regions are often found in spiral galaxies, including our own Milky Way. They can vary in size and temperature, and they play a crucial role in the process of star formation and the evolution of galaxies. Observing H II regions helps astronomers understand the lifecycle of stars and the dynamics of the universe.