A device is provided for temperature controlled heating of primarily solid food in a microwave oven, which includes a block of polymeric material which is thermally insulated with respect to the food and which is provided so as to be exposed to a same microwave radiation as the food. A heat sensitive, readable marking which corresponds to a temperature of the food is provided on a surface of the block of polymeric material. A reader is connected to a heating system of the oven, and reads the marking and transmits control signals to a control circuit for controlling the heating system of the oven, when the reader reads a change of the marking.