Nothing is sadder than an empty battery. All cold and lifeless, it needs rejuvenation. Luckily, morph mug battery gets juiced up by you filling up your cup as the morph mug battery gets hotter, it's energy level increases. This charming display of vitality also lets you know that your beverage is still hot hot. Mug measures 3-1/4 by 5 by 3-3/4-inch. Hand wash only. Do not microwave.