 These include, but are not limited to, ultraviolet-visible absorption, fluorescence and phosphorescence, mid-infrared, Raman, near-infrared, terahertz, and microwave, and atomic absorption, atomic emission, and laser-induced breakdown spectroscopies (and ICP-MS), as well as cutting-edge hyphenated and interdisciplinary techniques.Fundamental topics include, but are not restricted to, the theory of optical spectra and their interpretation, instrumentation design, and operational principles.Reports of spectral processing methodologies such as 2D correlation spectroscopy (2D-COS), baseline correction, and chemometric methods applied to spectra are also strongly encouraged.