What is the function of the pointer on a microscope?

Some microscopes, particularily those used in classrooms have a pointer as part of the eyepiece, which can be oriented to point at objects or features in the center of the field of view.

The purpose is, naturally enough, to point at things. It's most useful in teaching purposes, when you want to direct attention to one tiny detail or structure visible at any one time (i.e. a specific organelle).

Most professional scopes don't have pointers. I guess they figure that you should probably know what you're looking at by then. Sometimes it would be nice to point at something so you can get another opinion or even just show off something cool to someone else.