Zacharias Janssen is generally believed to be the first investigator to invent the compound microscope. However, because the accomplishment is generally agreed among historians to be dated in the 1590s, most scholars believe that his father, Hans, must have played an important role in the creation of the instrument. The pair worked together as spectacle makers in Middleburg, Holland not far from Hans Lippershey, another optical scientist who is often alternatively credited with the invention of the microscope.
The Dutch diplomat William Boreel was a longtime acquaintance of Zacharias Janssen, who had written to him about the device in letters. Boreel saw the microscope for himself, but only years later when it had already fallen into the hands of another family friend, Cornelius Drebbel. When the physician of the French King publicly sought information regarding the origin of the microscope during the 1650s, Boreel responded, relating information about the Janssens and recounting the device they had created and his experience surrounding its use.
The discovery of the light microscope in the late sixteenth
century by the Dutch optician Zacharias Janssen offered the possibility to study
the outer shape of small pieces of materials.