Because organisms present unique spectroscopic patterns, spectroscopic examination (e.g., Raman spectroscopy) of microorganisms (e.g., microbial cells) can help to differentiate between species and strains of microbes. Spectroscopic examination can also aid in the identification and measurement of subcellular processes (e.g., CO₂ production) that facilitate the understanding of cell growth, response to environmental stimuli, and drug actions.

The measurement of the absorption, emission, or scattering of electromagnetic radiation by atoms or molecules is referred to as spectroscopy. A transition from a lower energy level to a higher level with transfer of electromagnetic energy to the atom or molecule is called absorption; a transition from a higher energy level to a lower level results in the emission of a photon if energy is transferred to the electromagnetic field; and the redirection of light as a result of its interaction with matter is called scattering.

When atoms or...