Thermochromic materials change color in response to temperature variations. This property is due to the molecular structure of the materials, which alters when heated or cooled. Commonly used in products like mood rings and temperature-sensitive paint, these materials can provide visual cues about temperature changes. The technology behind thermochromism is often based on liquid crystals or dyes that react to heat. When the temperature rises or falls, the arrangement of these molecules shifts, resulting in a change in color. This feature is useful in various applications, including thermometers and packaging that indicates spoilage.