Hans Janssen was born in the 16th century, but his exact birthday is unknown. He is the father of Zacharias Janssen, who is thought to have been born in 1585 in The Hague.
Both Janssens are often credited with inventing the microscope, but many suspect that the real credit goes to the father, because the microscope was invented in 1590, when Zacharias was still a youngster. Other historians think that the inventor may have been Hans Lippershey, who filed the first patent for the telescope.
The general consensus among historians is that the Janssens invented the microscope, citing letters by Dutch diplomat William Boreel as evidence.
Interestingly, Hans and Zacharias Janssen lived in the same town as Hans Lippershey.