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-...