The mouse is a kind of rodent, and its size is large and small. There are many kinds, there are more than 450 kinds in the world. Mouse is one of the most primitive mammals in existence, which appeared in the age of dinosaurs. They are energetic, numerous, extremely fast in reproduction and highly adaptable. They can eat almost anything and live anywhere. Can dig holes, climb trees, climb mountains and wading, waste food, spread diseases, and do great harm to human beings, so it has been hit by human beings, but it is an animal family that can not be killed, so the word "mouse" has a mortar on its head, which means "can withstand being pounded". The reason why the mouse is honored as "old" is that it eats, drinks and plays all day, without working, just like a retired person. Ranked first in the zodiac.