The book "Photosensitizers in Medicine, Environment, and Security" offers a comprehensive examination of the synthesis of photosensitizers, focusing on innovative synthesis methods such as microwave treatment, sonochemistry, and the use of ionic liquids. It addresses the photochemistry and photophysics of these compounds both individually and in combination with nanoparticles. Furthermore, the application of photosensitizers in the fields of environmental protection, security, and medicine is discussed. The authors explore the common structures of photosensitizers that are advantageous for these applications, providing valuable insights into the versatile uses of these chemical compounds.