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This CSI is a fluorescing microscope. With the use of lasers, this scope helps scientists see three-dimensional structures in organic (living or formerly living) or inorganic matter. While optical and electron microscopes can also see in 3-D, the fluorescing scope provides better quality and greater detail.
So what is fluorescence? When organic or inorganic specimens absorb and then re-radiate light, the process is called photoluminescence (think of glow-in-the-dark paint or stickers that must be charged with light to glow). Fluorescence refers to the light that emits from the specimen only during its absorption of input light, not to the light that emits afterward.
Many specimens auto-fluoresce when hit with ultraviolet light. Others can be stained with fluorescing chemicals and then viewed under a microscope. The job of the fluorescing microscope is to make the non-fluorescing material in the object under view as dark as possible. The fluorescing areas, then, glow brightly against the darkness. Technically speaking, here's how that works: UV light is made by passing the visible light from the specimen through a filter. The filtered UV light illuminates the specimen, which then emits fluorescent light. The visible light from the specimen is then filtered through a barrier that only allows viewing of the fluorescent light.
Photo by Jeff Miller, © UW-Madison University Communications.