Yggdrasil

"Yggdrasil, the tree of the world. Guardian of wisdom and fate also."

- Johann Schmidt

The Yggdrasil is a figurative tree used by Asgardians to describe the cosmic nimbus that connects the Nine Realms. Each branch connects to one of the realms.

History
In 1942, when the HYDRA leader Johann Schmidt invaded the village of Tønsberg, Norway, he found the Tesseract hidden in the wall with a carving of the Yggdrasil Tree on it.

More than sixty years later, to explain Jane Foster the concept of the Nine Realms, Thor made a drawing of the Yggdrasil Tree in a sketch pad.