The present invention concerns an apparatus for staining tissue samples, said apparatus including a reagent section or reagent containers; at least one staining section or tissue samples, a robotic head or robotic element that may move reagent to a predetermined tissue sample, said robotic element being moveable above the reagent and the staining sections, a control element that may manage a staining process, a 2-D optical sensor to detect two-dimensional image data of a relevant property and that can feed the captured image data to the control element. By providing the robotic element with a 2-D optical sensor, a common image processor may be provided having multiple functions. By using a 2-D optical image processing system, the control system of the apparatus may easily be adapted to read various types of data presentations, just as actual images for sections of the apparatus may be identified in order to assess the condition of the apparatus. The optical sensor may be used to automatically identify the slides and the reagent containers present in the apparatus, just as the optical sensor may be used for checking if a slide is misplaced at or absent from a slide position, etc.