The natural emission of light by substances that have absorbed light energy, without being artificially treated with fluorescent dyes.
From 'auto-' (self) and 'fluorescence' (from Latin 'fluere,' to flow, and mineral fluorite). This optical term became important in microscopy and medical imaging.
Many living tissues glow naturally under certain light without any dye added—your fingernails, some parts of your eye, and many bacteria have autofluorescence, which scientists use to see things without staining them!
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