Color changing inks are special types of inks that can alter their color in response to different stimuli, such as temperature, light, or pH levels. These inks are often used in various applications, including security printing, packaging, and novelty items. The technology behind these inks typically involves microcapsules or chemical compounds that react to environmental changes. One common example of color changing ink is thermochromic ink, which changes color when exposed to heat. Another type is photochromic ink, which reacts to ultraviolet (UV) light. These inks not only add visual interest but also serve practical purposes, such as indicating temperature changes or enhancing product security.