How could you determine the size of an object that you are veiwing under a microscope?

I know how they do it in labs:


Small and very thin, transparent glass is positioned below the object you are watching. That glass has horizontal and vertical lines let's say 0.1mm apart and you can measure by that. For different magnifications they use finer or more coarse glasses.How could you determine the size of an object that you are veiwing under a microscope?
most substances are measured in micrometers. http://en.wikipedia.org/wiki/MicrometerHow could you determine the size of an object that you are veiwing under a microscope?
Use micrometer or nanometer.





For reticle with 1 cm/100 divisions, stereo microscope 1-4x gives about 100-25 microns per division (p%26lt;.03) and compound microscope 10-100x yields around 1-.1 micron per division (p%26lt;.03).





The scanning electron microscopes, X-ray reflection interface microscopes for advanced researches have a constant symbol of nano length to measure.





http://www.physorg.com/news82304881.htm
simple by knowing the power of lens u r using