Heat sensitive mugs are special types of drinkware that change color or reveal hidden images when filled with hot liquids. This effect is achieved through thermochromic materials, which react to temperature changes. When the mug is heated, the pigments in the coating alter their structure, resulting in a visual transformation. These mugs are popular for personal use and as gifts, often featuring fun designs or messages that become visible only when the mug is filled with a hot beverage. They are commonly used for coffee, tea, or hot chocolate, making them a playful addition to any kitchen or office setting.