What does thomas jefferson mean when he says "the tree of liberty must be refreshed from time to time with the blood of patriots and tyrants"?

it means that we must always be on guard against the ever expanding reach of the government and that if we expect to remain free we must be ready to fight to keep our freedom.

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

our former president bush did 9/11