Zacharias Janssen lived in Middleburg in the Netherlands from 1580 - 1638 according to History of the Microscope. He was a spectacle maker who is credited for inventing the first compound microscope. Since the achievement was thought to have occurred in the 1590s, some suggest that Janssen's father contributed to the discovery of the microscope. It is still debatable as to whether or not Janssen also invented the telescope.
Zacharias Janssen's microscope consisted of three draw tubes with lenses inserted into the ends of the flanking tubes. The eye piece and objective lens were both convex in different planes, which was an impressive and advanced technology at the time. Focusing on an object with the microscope was achieved by moving the draw tube in or out. The object could be magnified up to three times when the instrument was closed and up to ten times when the instrument was fully extended. Although there are no early models of Janssen's microscope that are preserved, there is a similar construction in the Middleburg Museum in the Netherlands that historians attribute to Janssen. Although the construction of this initial microscope is very basic compared to the instruments used today, the basic application of such an advanced structure of lenses during this time period is what makes this contribution significant in history.