An encryption system constructed by pillar[5]arene, spiropyran and pentanenitrile (free state and grafted to polymer) was constructed by Wang et al. After UV irradiation, spiropyran would transform into merocyanine. When the visible light was shined on the material, the merocyanine close to the pillar[5]arene-free pentanenitrile complex had faster transformation to spiropyran; on the contrary, the one close to pillar[5]arene-grafted pentanenitrile complex has much slower transformation rate. This spiropyran-merocyanine transformation can be used for message encryption. Another strategy is based on the metallacages and polycyclic aromatic hydrocarbons. Because of the fluorescnece emission differences between the complex and the cages, the information could be encrypted.