While there's no single definitive inventor of the optical microscope, Zacharias Janssen is often credited with creating the first compound microscope around 1590.

However, it's important to note:

* Cornelis Drebbel also claimed to have invented a compound microscope around the same time.

* Galileo Galilei developed a compound microscope in 1609, though it was simpler than Janssen's.

* Antonie van Leeuwenhoek, though not an inventor of the microscope itself, made significant contributions by developing powerful single-lens microscopes and using them to make groundbreaking observations of microscopic organisms.

Therefore, while Zacharias Janssen is often considered the inventor, the history of the microscope is complex and involves contributions from various individuals.