Abstract: An incubating device particularly adapted for aligning an array of microscope slides bearing a tissue section, sample or specimen, and incubating the same with a series of test or reagent solutions at a higher-than-ambient temperature, is disclosed. The incubating device has a main body including a recess which substantially forms a tray in the main body. A plurality of substantially regularly spaced metal blocks are disposed in the recess, and a substantially flat upper surface of each metal block is adapted to receive and be in contact with a respective microscope slide.A heater is mounted underneath the main body to heat the main body, and to affect by direct conductance of heat, the heating of the metal blocks. A thermostat is mounted to the main body to monitor the temperature of the main body and to regulate the output of the heater in response thereto whereby the temperature of the metal blocks is maintained in a desired predetermined range.