thomas kinkade (the polar express) heat-sensitive mug morphing mugs seeing is believing, but sometimes the most real things in the world are the things we can't see.” bring the magic of the polar express to every cup of coffee with this morphing mugs heat-sensitive, color changing mug that features an image of the north pole by tk studios in the artist’s instantly recognizable style. the exterior of this officially licensed 11oz mug illuminates from black as hot liquid is added, revealing the hidden image in full vivid colors. *while this mug may be used in the dishwasher or microwave, for the longest lasting, highest quality product, we strongly recommend against it.