The Tree of Life Symbolism - World Tree / Gaia FolkLore
From Ancient Celtic Lore comes the concept that all living things arise from the Great Mother, Gaia, source of Life and nourishment. She is often depicted as a vessel or pot, roundish for the earth which she represents, a cradle from which arises the World Tree, The Tree of Life. Though each tree had a different meanings to the ancient Celts the tree was uniformly venerated as a source of wisdom and hope, an enduring link between the upper and lower worlds, a reminder of the eternal cycle of Life & the Seasons. It roots are deep in the earth and its branches stretched to the heavens. Its trunk exists within this realm. The Tree of Life serves as a simultaneous reminder of our roots and our destination. As it is above, so it is below with half of its being in light and the other half in darkness, half in air and fire and half in water and earth, half male and half female.

In Norse mythology, Yggdrasil ("The Terrible One's Horse"), also called the World Tree, is the giant ash tree that links and shelters all the worlds. Beneath the three roots the realms of Asgard, Jotunheim, and Niflheim are located.