Transmitted light

You've probably done this type of microscopy looking at tissue culture cells. In brightfield, light passes through the specimen, some is absorbed/scattered and an image is formed from what passes through.

Contrast is improved with techniques such as phase contrast or DIC. Tissue samples can be stained with dyes (eg H&E) or with immuno-histochemistry and colour images can be captured on either the Axio Imager or the stereoscope.