Polymorph is a plastic material that melts/becomes soft at 62 degrees celcius. It also becomes transparent at this temperature. When it cools down, it becomes hard and non-transparent again.
The polymorph thermostat can control an electric kettle or an electric plate so that when it is filled with water, its temperature is kept constant at 62 degrees or any other temperature you set. This allows you to throw your polymorph plastic bits into the water, and take them out when they are completely soft and transparent.
The box has one 220V power input, one output that is turned on when the temperature controller senses that it is too cold outside.