1) The Mongol Empire, under the leadership of Genghis Khan, became the largest contiguous empire in history, spanning from Asia to Europe.

2) The Federal Reserve System, often referred to as the Fed, is the central banking system of the United States.

3) The first successful portable MP3 player, the Diamond Rio PMP300, was released in 1998 and could hold up to 60 minutes of music.

4) The world's largest ocean, the Pacific Ocean, covers an area of approximately 63 million square miles.