who invented the microscope

Early in the 1500's a couple of glasses makers experimented with lenses and realized that if they combined lenses that whatever was being viewed was magnified even more. There names were Zaccharias Jepssen and his father. This is commonly considered the first rudimentary compound microscope.

However, it was Galileo who improved upon their work adding a focusing device. Later, a more standardized version was developed by Anthony Leeuwenhoek as he determined that by grinding and shaping the lenses, he could produce even greater magnification.