You snap the metal tab to heat this up. It works well, is heart-shaped, and is discreet due to the shape. It can be used anywhere, at any time. I love it, it's also perfect to use for any kind of muscle ache or massage that you may need. It can be easy to put away. I will definitely be ordering more in the future. This is a perfect gift to hand out for other people in your family who have muscle aches. The amazing thing about this product is that you can use it on anyone because it's essentially a hand or muscle warmer.