Color-changing inks are special types of inks that can alter their color in response to various stimuli, such as temperature, light, or pH levels. These inks are often used in applications like security printing, where they help prevent counterfeiting, or in novelty items that change color when exposed to heat or sunlight. The technology behind color-changing inks typically involves the use of thermochromic or photochromic materials. Thermochromic inks change color when they are heated or cooled, while photochromic inks react to changes in light intensity. These innovative inks offer exciting possibilities for creative design and functional applications.