This interdisciplinary work gives a comprehensive survey of the state of the art: from applications and trends in fluorescence techniques in science to medicine and engineering. It covers fields like environmental and materials science, biology, medicine, physics and chemistry. Moreover, it reports about methods such as ultra-fast time-resolved or single molecule spectroscopy and gives examples of applications in the fields of electroluminescent polymers. Visualization of membrane potentials in neurons or fluorescence imaging of the brain are described by the authors.