A device (20) for processing tissue samples has a processing room (22) for introducing and processing the tissue samples (20). A chamber (34) communicates with the processing room (22). At least one filling level sensor (28, 30, 32) detects a measurement value which is representative of a filling level of a liquid in the chamber (34). A calculating unit determines a filling level of the liquid in the processing room (22) depending on the filling level of the liquid in the chamber (34).