Sub Solution does come with a patented heat activator. The Lithium Chloride granules are the best way to raise the temperature of Sub Solution to the room temperature. Nonetheless, you can microwave Sub Solution. Mix the whole thing and put it in the microwave for about 10 seconds. You will be able to read the temperature on the temperature strip you get on the Sub Solution's plastic contained. Make sure it's between 94F and 100F.