<正>Thermochromic polymers will play an extremely important role in the next future. The physical background of theimochromism and the state of development of thermochromic polymers based on light absorption effects are reported. In detail, the interactions between the polymer matrix and the thermochromic composite- composed of leuco or indicator dyes -are discussed on a molecular level. Thermochromic hydrogels with extremely high transparency, an outstanding switching behavior from colorless to colored or between different colors is presented. Preparation of thermosetting and thermoplastic polymers, including the resulting optical, and, for the first time, the mechanical properties are discussed in relation to matrix tuned high-resistant microcapsules.