Why is it called the interior great wall?

Why they built the Great Wall of China?

Built to protect states from being attacked by other states during the Warring States Period, and to defend China against attack from Mongolians from the Qin Dynasty to the Ming Dynasty.

aug 15, 2012 - although van leeuwenhoek was not the inventor of the microscope, he advanced it more he loved to grind and focus a new lens in order to see the unseen world. most of leeuwenhoek's microscopes were silver. in a simple but significant experiment (1668), he demonstrated that worms found on