6. Vatican City explained (History/World Culture): Using drawings and historical photos, this historian simplifies world issues in a fun way, allowing for open discussion.   7. Super expensive metals (Science): Inside a Noble Metals factory, where even the dust on your shoes is too valuable to ignore! Make the Periodic Table of Elements come to life.   8. Grammaropolis noun song (English/Language Arts): Think of this as an updated Schoolhouse Rock.   9. Negative numbers introduction (Math): Khan Academy incorporates real world examples into a very basic math concept explanation.   10. Is Pluto a planet? (History/Science): Learn about how Pluto came to be called a planet based on historical definitions and scientific inventions, to its eventual fall from the planet category. pluto