An apparatus for staining sample sections, comprising: a chamber that is adapted for fastening sample sections therein and a pump that is adapted for pumping liquids through the chamber. The chamber has an inlet and an outlet. The inlet can be connected to at least one reservoir of a staining liquid via inlet lines that are controllable by valves. The inlet lines are formed at least in the region of the associated valves by means of elastic hose lines, and the valves are formed as hose pinch valves. This apparatus minimizes or eliminates contaminations arising from staining processes for thin sections that are in particular prepared for examination in an electron microscope.