@fify-- Actually, there are stages that heat up, but the microscope has to be a special one that has a heating chamber on it. When you put a specimen on a heat insulating stage and turn the heating chamber on, the stage heats up and so does the specimen. It's possible to go up to seven hundred degrees celsius with it but that's usually not necessary.
I believe these stages were produced to examine how something went from solid to fluid form and to determine melting points of substances. I don't know if there are any cooling stages or microscopes yet.