In Norse mythology, the nine realms connected by the world tree Yggdrasil are Atgard, Midgard, Vanaheim, Alfheim, Svartalfheim, Niflheim, Muspelheim, Helheim, and Jotunheim. Each realm represents a distinct aspect of existence, inhabited by various beings, including gods, giants, and spirits. Yggdrasil serves as the cosmic tree linking these realms, symbolizing the interconnectedness of all creation. Its significance emphasizes the delicate balance of life across the cosmos and the intricate relationships among its inhabitants.