Pen knives, diminutive pocket knives with small sharp blades, derive their name from their original purpose: to slice through quill tips and turn them into writing pens.
Chameleons change their colors using chromatophores, a specialized type of cell that contains tiny sacs of pigments; when a chameleon shifts color, they do so by expanding or contracting these sacs to change the color of the cells.
The highest uninterrupted waterfall in the world is Angel Falls, located in Venezuela. It has a total height of 3,212 feet (979 meters) and a plunge of 2,648 feet (807 meters).
Writers for That ’70s Show got creative with their titles as the show progressed; all the episode titles in season five were the titles of Led Zeppelin songs, in season six they were The Who songs, in season seven they were The Rolling Stones songs, and in season eight they were Queen songs.