1) In Norse mythology, the World Tree, known as Yggdrasil, is a massive ash tree that connects the nine realms of existence. It is considered the center of the cosmos and serves as a conduit between different realms, including Asgard (realm of the gods), Midgard (realm of humans), and Helheim (realm of the dead).

2) The word "oxygen" contains two vowels: O and E.

3) The Treaty of Versailles, signed in 1919, officially ended World War I and imposed heavy penalties and reparations on Germany.

4) Will Smith is an American actor, rapper, and producer known for his roles in films such as "Men in Black," "Independence Day," and "The Pursuit of Happyness." He has achieved success in both the music and film industries and has received numerous accolades for his work.