A system and method for treatment of biological samples is disclosed. In some embodiments, an automated biological sample staining system (100), comprising at least one microfluidic reagent applicator (118); at least one bulk fluid applicator (116); at least one fluid aspirator; at least one sample substrate holder; at least one relative motion system; and a control system (102) that is programmed to execute at least one staining protocol on a sample mounted on a substrate that is held in the at least one sample substrate holder.