What could humans see before the invention of the microscope?
Microscopes were invited by Zacharias Janssen in 1590, but before that, the smallest thing a human could see was the length of a human hair.
If nobody ever knew that there was something smaller than what you could see with just your eyes, why would you bother even thinking about it? However once it was possible to see smaller and smaller things, who knew what the limits were! Because microscopes allowed humans to finally see past our eye’s abilities, a whole new world was opened up. Cells are at microscopic level of small so you couldn’t even see them without a microscope. They allowed cells to be seen, which would then lead to the experiments and questions that would develop into our current understanding of cell biology.