Ive often thought that a realistic discovery that could have accelerated human science would have been optical grade glass during Greek period.

So many discoveries came from magnification of the very small and the very distant.

Another early microscopy person is Leeuwenhoek who started work in the 1670's. I learned of Leeuwenhoek reading "I Contain Multitudes" by Ed Yong.

https://en.wikipedia.org/wiki/Antonie_van_Leeuwenhoek#Recogn...

https://lensonleeuwenhoek.net/content/hair-mouse-bear-human-...

In the annals of microscopy, the name of Jan Swammerdam, an early pioneer of the microscope, is often overshadowed by more famous contemporaries like Antonie van Leeuwenhoek and Robert Hooke. Swammerdam, a Dutch naturalist and physician, was a meticulous observer and experimenter whose contributions to the field of microscopy in the 17th century were groundbreaking. His groundbreaking work on insect anatomy laid the foundation for modern entomology, and his innovative dissection techniques enabled him to reveal the inner workings of living organisms with remarkable clarity.

https://en.wikipedia.org/wiki/Jan_Swammerdam