Spectral information may be employed in process control and/or quality control of goods and articles. Spectral information may be employed in process control and/or quality control of media, for example financial instruments, identity documents, legal documents, medical documents, financial transaction cards, and/or other media, fluids for example lubricants, fuels, coolants, or other materials that flow, and in machinery, for example vehicles, motors, generators, compressors, presses, drills and/or supply systems. Spectral information may be employed in identifying biological tissue and/or facilitating diagnosis based on biological tissue.