For heat therapy, place the heat & cold pack inside a 600W microwave oven for no more than 25 seconds (if the Pack is at room temperature) or 1 minute (if the Pack is frozen). After that, check to ensure that the temperature is not too hot for the skin. Alternatively, immerse the Heat & Cold Pack into hot water (90°C) for approximately 10 minutes (time can be adjusted according to personal preference). As for cold therapy, keep the Heat & Cold Packs in the fridge for approximately 1 hour.