Thermal indicators are devices or materials that visually show temperature changes. They often change color or display a specific pattern when exposed to different heat levels. Common examples include thermochromic inks and temperature-sensitive stickers, which are used in various applications, from food packaging to medical devices. These indicators help monitor temperature conditions, ensuring safety and quality. For instance, in the food industry, thermal indicators can signal if a product has been stored at unsafe temperatures, helping to prevent spoilage or foodborne illnesses. Their simplicity and effectiveness make them valuable tools in many fields.