A portable, self-contained heating and cooling assembly comprising at least two compartments or alternately one compartment and a heat reservoir wherein the two compartments are specifically structured to concurrently hold containerized liquids, medical items or objects, foodstuffs, etc. Thermoelectric heat transfer technology is utilized to transfer heat energy between the two compartments by means of a thermoelectric device which, when electrically activated, serves to remove heat from one compartment and the object or substance therein and transfer such heat to the other compartment as well as the object or substance therein thereby serving to simultaneously cool the interior of one compartment and heat the interior of the other compartment. Operative modifications include the selective heating or cooling of a single object or substance within one compartment which may be interconnected in thermal contact with a second compartment or with the thermal reservoir.