Star birth occurs in vast clouds of gas and dust known as nebulae. Within these clouds, regions of higher density can collapse under their own gravity, leading to the formation of a protostar. As the protostar gathers more material, its core heats up, eventually reaching temperatures sufficient for nuclear fusion to begin. Once nuclear fusion ignites, the protostar transforms into a main-sequence star, entering a stable phase of its life cycle. This process can take millions of years, and the newly formed star will continue to shine for billions of years, depending on its mass and composition.