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 invention of the transistor by Bell Laboratories in 1947 revolutionized electronics and paved the way for the development of smaller, more efficient electronic devices.

3) The world's first stock exchange was established in Amsterdam in 1602.

4) The smallest unit of time is known as a zeptosecond, which is equal to one trillionth of one billionth of a second.