Can any cell be viewed under a light microscope?

This primarily depends on the optical power of the microscope. If you take an ordinary educational microscope, then any cell there is quite difficult to see. But nowadays there are microscopes, thanks to which it was possible to photograph an atom. So now any cell can be examined in a microscope in some detail. Electron microscopes are mainly used. They are not limited only by the strength of lens bending and small focal lengths. Therefore, thanks to such microscopes, many discoveries have been made.