Every material has its own characteristic absorption and emission spectrum.
By selective excitation using specific wavelengths, it is possible to identify materials with high certainty, even if only small traces exist.

Spectroscopy is used in the research of molecules by optically exciting the molecules. It is one of the most important tools in the research of the structure of matter.

The laser allows the use of definite controlled wavelengths, which results in a very high resolution measurements. Increasing the accuracy of the determination of the wavelength allows a distinction between smaller details in the material structure.

Photo-chemistry is the science of chemical changes which are the result of light.

Examples are:

• "Tanning" of the skin in the sun light.
• Photosynthesis in plants.
• The process of vision within the retina cells of the eye.
• Induced fluorescence is a very sensitive process, which allows selective excitation of specific energy levels in a specific molecule. This process is used in forensic science to identify trace residuals of molecules.